[analyzer] Add plist output checks for all four "path notes" tests.

[analyzer] Add plist output checks for all four "path notes" tests.

No functionality change, but from now on, any new path notes should be
tested both with plain-text output (for ease of human auditing) and with
plist output (to ensure control flow and events are being correctly
represented in Xcode).

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@161351 91177308-0d34-0410-b5e6-96231b3b80d8