[WFLY-2390] Don't discard existing flags in withFlag(s)
[WFLY-2370] Block quick management callers to give ServerInventory a chance to initialize
[WFLY-490] / [WFLY-2394] Preventing any current AccessControlContext which may also be associated with a caller from being associated with any Thread created to execute the task.
[WFLY-490] / [WFLY-2394] Propagate the Subject over to the Thread executing the task.
Fix test's algorithm for awaiting HC start