[analyzer]RetainCount: Fix an autorelease related false positive.

The Cnt variable is adjusted (incremented) for simplification of
checking logic. The increment should not be stored in the state.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@174104 91177308-0d34-0410-b5e6-96231b3b80d8