[HeaderSearch] Make sure we clear the mapped name from the LookupFileCacheInfo when we reset the start point.

rdar://16462455

git-svn-id: http://llvm.org/svn/llvm-project/cfe/trunk@205071 91177308-0d34-0410-b5e6-96231b3b80d8
[test] Add a RUN line to get a hint on why the test is failing at the buildbots.

git-svn-id: http://llvm.org/svn/llvm-project/cfe/trunk@205072 91177308-0d34-0410-b5e6-96231b3b80d8