lxd/network/acl: Use the journalctl wrapper script introduced in th…

…e LXD snap

This way, we rely on the `journalctl` host binary and not on the one shipped within the snap (which the version might differ whether LXD uses core22 or core24 as a base snap)
We can also remove the `--directory ..` flag as the wrapper script which executes the host journalctl targets by default the host journal directory.

Signed-off-by: Gabriel Mougard <gabriel.mougard@canonical.com>
(cherry picked from commit 0217e14)

lxd/network/acl/acl_ovn.go

@@ -1163,9 +1163,8 @@ func ovnParseLogEntry(logline string, syslogTimestamp string, prefix string) str
 func ovnParseLogEntriesFromJournald(ctx context.Context, systemdUnitName string, filter string) ([]string, error) {
 	var logEntries []string
 	cmd := []string{
-		"/usr/bin/journalctl",
+		"journalctl",
 		"--unit", systemdUnitName,
-		"--directory", shared.HostPath("/var/log/journal"),
 		"--no-pager",
 		"--boot", "0",
 		"--case-sensitive",