[sanitizer] Intercept getmntent, getmntent_r.


git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@192959 91177308-0d34-0410-b5e6-96231b3b80d8
[asan] fix a test on Mac

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@192960 91177308-0d34-0410-b5e6-96231b3b80d8