Fix data race in Linux compress maintainer tests

TestCompressMaintainOwner and TestCompressMaintainMode waited for the
background compression goroutine with a fixed sleep before reading
state it writes (the fakeFS owner map and the compressed file). The
sleep established no happens-before relationship, so the race detector
reported a data race on Linux, where these tests run.

Replace the sleep with l.Close(), which now flushes the pending
compression and joins the mill goroutine, synchronizing its writes
with the subsequent assertions. This also makes the tests
deterministic rather than relying on a timing window.

Signed-off-by: Antonin Bas <antonin.bas@broadcom.com>
Co-authored-by: Cursor <cursoragent@cursor.com>

Author: antoninbas

linux_test.go

@@ -7,7 +7,6 @@ import (
 	"os"
 	"syscall"
 	"testing"
-	"time"
 )
 
 func TestMaintainMode(t *testing.T) {
@@ -115,9 +114,10 @@ func TestCompressMaintainMode(t *testing.T) {
 	err = l.Rotate()
 	isNil(err, t)
 
-	// we need to wait a little bit since the files get compressed on a different
-	// goroutine.
-	<-time.After(10 * time.Millisecond)
+	// Closing flushes the pending compression and waits for the mill
+	// goroutine to exit, which also synchronizes its writes with the
+	// assertions below.
+	isNil(l.Close(), t)
 
 	// a compressed version of the log file should now exist with the correct
 	// mode.
@@ -165,9 +165,10 @@ func TestCompressMaintainOwner(t *testing.T) {
 	err = l.Rotate()
 	isNil(err, t)
 
-	// we need to wait a little bit since the files get compressed on a different
-	// goroutine.
-	<-time.After(10 * time.Millisecond)
+	// Closing flushes the pending compression and waits for the mill
+	// goroutine to exit, which also synchronizes its writes to fakeFS with
+	// the assertions below.
+	isNil(l.Close(), t)
 
 	// a compressed version of the log file should now exist with the correct
 	// owner.