Fix regex operator precedence bug in freenas_api_call method guard

'! $method =~ /pattern/' is parsed as '(! $method) =~ /pattern/' due to
precedence, so the regex ran against "" and always returned false. The
guard never fired and any method string passed through to the API call.

Changed to '$method !~ /^(?:GET|DELETE|POST)$/' which correctly tests the
method string. Also replaced atomic group (?>...) with non-capturing (?:...)
since there is no backtracking concern here.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

perl5/PVE/Storage/LunCmd/FreeNAS.pm

@@ -464,7 +464,7 @@ sub freenas_api_call {
     syslog("info", (caller(0))[3] . " : called for host '" . $apihost . "'");
 
     $method = uc($method);
-    if (! $method =~ /^(?>GET|DELETE|POST)$/) {
+    if ($method !~ /^(?:GET|DELETE|POST)$/) {
         syslog("info", (caller(0))[3] . " : Invalid HTTP RESTful service method '$method'");
         die "Invalid HTTP RESTful service method '$method' used.";
     }