[analyzer][UninitializedObjectChecker] Fixed a false negative by no longer filtering...

[analyzer][UninitializedObjectChecker] Fixed a false negative by no longer filtering out certain constructor calls

As of now, all constructor calls are ignored that are being called
by a constructor. The point of this was not to analyze the fields
of an object, so an uninitialized field wouldn't be reported
multiple times.

This however introduced false negatives when the two constructors
were in no relation to one another -- see the test file for a neat
example for this with singletons. This patch aims so fix this issue.

Differential Revision: https://reviews.llvm.org/D48436

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@339237 91177308-0d34-0410-b5e6-96231b3b80d8