Revert "[sanitizer] Fix race condition in GetNamedMappingFd with decorate_pro…" (#194271)
Reverts llvm/llvm-project#190981 due to buildbot failure
(https://lab.llvm.org/buildbot/#/builders/66/builds/29993):
```
SanitizerCommon-asan-i386-Linux :: Linux/decorate_proc_maps.cpp
```