tests: make flock check in tests/main/snap-remove-terminate more robu…

…st (#14514)

* tests: make flock check in tests/main/snap-remove-terminate more robust

The flock check was testing that the service just created has held the
flock immediately. In some cases the test service wasn't able to hold
the lock fast enough.

Instead, check that a file is created by the service to confirm the
snap is run by the service.

Signed-off-by: Zeyad Gouda <zeyad.gouda@canonical.com>

* tests: fix shellcheck

Signed-off-by: Zeyad Gouda <zeyad.gouda@canonical.com>

* tests: address review comments

Signed-off-by: Zeyad Gouda <zeyad.gouda@canonical.com>

---------

Signed-off-by: Zeyad Gouda <zeyad.gouda@canonical.com>

tests/main/snap-remove-terminate/task.yaml

@@ -15,14 +15,17 @@ restore: |
     systemctl stop test-kill.service || true
     systemctl reset-failed test-kill.service || true
 
+debug: |
+    journalctl -u test-kill.service
+
 execute: |
     echo "Start a long running process"
     lockfile="$(pwd)/lockfile"
     touch "$lockfile"
     sh_snap_bin="$(command -v test-snapd-sh.sh)"
-    systemd-run --unit test-kill.service flock "$lockfile" "$sh_snap_bin" -c "sleep 100000"
+    systemd-run --unit test-kill.service flock "$lockfile" "$sh_snap_bin" -c 'touch /var/snap/test-snapd-sh/common/alive; sleep 100000'
     # Wait for service to be up
-    retry -n 10 systemctl is-active test-kill.service
+    retry -n 10 test -f /var/snap/test-snapd-sh/common/alive
 
     echo "Lock is held"
     not flock --timeout 0 "$lockfile" --command "true"