fix(tests/common/lib.sh): Support set -e in test scripts

The `systemctl is-active virtualbox-guest-utils.service` command returns
a non-zero exit status when the service is inactive, causing early exit
in tests that use `set -e`.

This change suppresses that error with `|| true` to prevent test failure
when the service check returns non-zero.

Fixes this test:

```
root@demo:~/sanoid/tests/syncoid# cat /tmp/syncoid_test_run_011_sync_out-of-order_snapshots.log
+ set -e
+ . ../../common/lib.sh
+++ uname
++ unamestr=Linux
+ POOL_IMAGE=/tmp/jimsalterjrs_sanoid_815.img
+ POOL_SIZE=64M
+ POOL_NAME=jimsalterjrs_sanoid_815
+ truncate -s 64M /tmp/jimsalterjrs_sanoid_815.img
+ zpool create -m none -f jimsalterjrs_sanoid_815 /tmp/jimsalterjrs_sanoid_815.img
+ trap cleanUp EXIT
+ zfs create jimsalterjrs_sanoid_815/before
+ zfs snapshot jimsalterjrs_sanoid_815/before@this-snapshot-should-make-it-into-the-after-dataset
+ disableTimeSync
+ which timedatectl
+ '[' 0 -eq 0 ']'
+ timedatectl set-ntp 0
+ which systemctl
+ '[' 0 -eq 0 ']'
+ systemctl is-active virtualbox-guest-utils.service
inactive
+ cleanUp
+ zpool export jimsalterjrs_sanoid_815
+ rm -f /tmp/jimsalterjrs_sanoid_815.img
```

tests/common/lib.sh

@@ -57,7 +57,7 @@ function disableTimeSync {
 
     which systemctl > /dev/null
     if [ $? -eq 0 ]; then
-        systemctl is-active virtualbox-guest-utils.service && systemctl stop virtualbox-guest-utils.service
+        systemctl is-active virtualbox-guest-utils.service && systemctl stop virtualbox-guest-utils.service || true
     fi
 }