[FIX] service dialogs: Add "modal" busy spinner on serviceDialogs when form has been submitted.
Similar functionality was added to 13.x a while back but handled differently in Bootstrap, so not a direct backport.

git-svn-id: file:///var/local/code.tiki.org/tikisvn/branches/12.x@52305 b456876b-0849-0410-b77d-98878d47e9d5