[analyzer] Toning down invalidation a bit

When a function takes the address of a field the analyzer will no longer
assume that the function will change other fields of the enclosing structs.

Differential Revision: https://reviews.llvm.org/D57230


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@352473 91177308-0d34-0410-b5e6-96231b3b80d8