cert deploy fails if re-keyed

[Sander-agfa]

A certificate (re-)deploy fails if the key has changed,
and certificate filename timestamping is disabled.
this bug can be worked around if you enable timestamping on the certificate filenames,
or if you temporarily delete/set another certificate/key in the active profile.

Error Received from the REST call:

02/19/2019:10:02:09 restCall():/usr/bin/curl -sk --connect-timeout 5 -m 120 -H Content-Type: application/json --user letsencrypt:*********** https://***********/mgmt/tm/sys/crypto/key -X POST -d "{ "command": "install", "name": "/Common/HOSTNAMEHEREkey", "from-local-file": "/var/config/rest/downloads/HOSTNAMEHERE.key", "securityType": "normal" }"
02/19/2019:10:02:10 createCertFromUpload()[Write Back Results]: {
"apiError": 3,
"code": 400,
"errorStack": [],
"message": "01070317:3: profile /Common/HOSTNAMEHERE's key and certificate do not match"
}

[Sander-agfa]

Latest commit in #10 Fixes this issue.
Adds the timestamp once, even if timestamping is disabled if it detects this "key and cert do not match" error.