tsan: remove in_rtl counter

This is intended to address the following problem.
Episodically we see CHECK-failures when recursive interceptors call back into user code. Effectively we are not "in_rtl" at this point, but it's very complicated and fragile to properly maintain in_rtl property. Instead get rid of it. It was used mostly for sanity CHECKs, which basically never uncover real problems.
Instead introduce ignore_interceptors flag, which is used in very few narrow places to disable recursive interceptors (e.g. during runtime initialization).



git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@197979 91177308-0d34-0410-b5e6-96231b3b80d8