Unmount less aggressively in destroy script

[rcsanchez97]

As I was creating and removing chroots I noticed that if two chroots are named such that the name of one chroot is a strict substring of the other, calling the destroy script of the chroot with the shorter name will invoke umount for all mount points mounted in both chroots. This proposed changes makes the umount invocation more precise.

Before this change:

roberto@build01:~/alpine-chroot-install (master =)$  sudo ./alpine-chroot-install -d /var/lib/chroot/alpine-test
[output omitted]

roberto@build01:~/alpine-chroot-install (master =)$  sudo ./alpine-chroot-install -d /var/lib/chroot/alpine-test2
[output omitted]

roberto@build01:~/alpine-chroot-install (master =)$  ls -d /var/lib/chroot/alpine-test*
/var/lib/chroot/alpine-test  /var/lib/chroot/alpine-test2

roberto@build01:~/alpine-chroot-install (master =)$  ls -d /var/lib/chroot/alpine-test*
/var/lib/chroot/alpine-test  /var/lib/chroot/alpine-test2

roberto@build01:~/alpine-chroot-install (master =)$  sudo /var/lib/chroot/alpine-test/destroy --remove
Unmounting /var/lib/chroot/alpine-test2/sys/kernel/tracing
Unmounting /var/lib/chroot/alpine-test2/sys/kernel/security
Unmounting /var/lib/chroot/alpine-test2/sys/kernel/debug
Unmounting /var/lib/chroot/alpine-test2/sys/kernel/config
Unmounting /var/lib/chroot/alpine-test2/sys/fs/pstore
Unmounting /var/lib/chroot/alpine-test2/sys/fs/fuse/connections
Unmounting /var/lib/chroot/alpine-test2/sys/fs/cgroup
Unmounting /var/lib/chroot/alpine-test2/sys/fs/bpf
Unmounting /var/lib/chroot/alpine-test2/sys
Unmounting /var/lib/chroot/alpine-test2/proc
Unmounting /var/lib/chroot/alpine-test2/home/roberto/alpine-chroot-install
Unmounting /var/lib/chroot/alpine-test2/dev/shm
Unmounting /var/lib/chroot/alpine-test2/dev/pts
Unmounting /var/lib/chroot/alpine-test2/dev/mqueue
Unmounting /var/lib/chroot/alpine-test2/dev/hugepages
Unmounting /var/lib/chroot/alpine-test2/dev
Unmounting /var/lib/chroot/alpine-test/sys/kernel/tracing
Unmounting /var/lib/chroot/alpine-test/sys/kernel/security
Unmounting /var/lib/chroot/alpine-test/sys/kernel/debug
Unmounting /var/lib/chroot/alpine-test/sys/kernel/config
Unmounting /var/lib/chroot/alpine-test/sys/fs/pstore
Unmounting /var/lib/chroot/alpine-test/sys/fs/fuse/connections
Unmounting /var/lib/chroot/alpine-test/sys/fs/cgroup
Unmounting /var/lib/chroot/alpine-test/sys/fs/bpf
Unmounting /var/lib/chroot/alpine-test/sys
Unmounting /var/lib/chroot/alpine-test/proc
Unmounting /var/lib/chroot/alpine-test/home/roberto/alpine-chroot-install
Unmounting /var/lib/chroot/alpine-test/dev/shm
Unmounting /var/lib/chroot/alpine-test/dev/pts
Unmounting /var/lib/chroot/alpine-test/dev/mqueue
Unmounting /var/lib/chroot/alpine-test/dev/hugepages
Unmounting /var/lib/chroot/alpine-test/dev
Removing /var/lib/chroot/alpine-test

roberto@build01:~/alpine-chroot-install (master =)$  ls -d /var/lib/chroot/alpine-test*
/var/lib/chroot/alpine-test2

After the change, the sudo /var/lib/chroot/alpine-test/destroy --remove produces output like this:

roberto@build01:~/alpine-chroot-install (master >)$  sudo /var/lib/chroot/alpine-test/destroy --remove
Unmounting /var/lib/chroot/alpine-test/sys/kernel/tracing
Unmounting /var/lib/chroot/alpine-test/sys/kernel/security
Unmounting /var/lib/chroot/alpine-test/sys/kernel/debug
Unmounting /var/lib/chroot/alpine-test/sys/kernel/config
Unmounting /var/lib/chroot/alpine-test/sys/fs/pstore
Unmounting /var/lib/chroot/alpine-test/sys/fs/fuse/connections
Unmounting /var/lib/chroot/alpine-test/sys/fs/cgroup
Unmounting /var/lib/chroot/alpine-test/sys/fs/bpf
Unmounting /var/lib/chroot/alpine-test/sys
Unmounting /var/lib/chroot/alpine-test/proc
Unmounting /var/lib/chroot/alpine-test/home/roberto/alpine-chroot-install
Unmounting /var/lib/chroot/alpine-test/dev/shm
Unmounting /var/lib/chroot/alpine-test/dev/pts
Unmounting /var/lib/chroot/alpine-test/dev/mqueue
Unmounting /var/lib/chroot/alpine-test/dev/hugepages
Unmounting /var/lib/chroot/alpine-test/dev
Removing /var/lib/chroot/alpine-test