[analyzer] Change the way in which IDC Visitor decides to kick in and make sure it...

[analyzer] Change the way in which IDC Visitor decides to kick in and make sure it attaches in the given edge case

In the test case below, the value V is not constrained to 0 in ErrorNode but it is in node N.
So we used to fail to register the Suppression visitor.

We also need to change the way we determine that the Visitor should kick in because the node N belongs to
the ExplodedGraph and might not be on the BugReporter path that the visitor sees. Instead of trying to match the node,
turn on the visitor when we see the last node in which the symbol is ‘0’.

llvm-svn: 177121