[Analyzer] Iterator Checker Hotfix: Defer deletion of container data until its...

[Analyzer] Iterator Checker Hotfix: Defer deletion of container data until its last iterator is cleaned up

The analyzer may consider a container region as dead while it still has live
iterators. We must defer deletion of the data belonging to such containers
until all its iterators are dead as well to be able to compare the iterator
to the begin and the end of the container which is stored in the container
data.

Differential Revision: https://reviews.llvm.org/D48427

llvm-svn: 338234