Canonicalize some aspects of the folly/experimental/hazptr test
Canonicalize some aspects of the folly/experimental/hazptr test

Summary:
[Folly] Canonicalize some aspects of the `folly/experimental/hazptr` test.

* Remove the custom `main()` and use the provided weak symbol, either from `folly/test/common/TestMain.cpp` or from `gtest` depending on the build.
* Extract some common setup/teardown (just debug logging in this case) to a test fixture.

Reviewed By: Orvid

Differential Revision: D4234154

fbshipit-source-id: 25613cba0ad6c9147714d98150e013fba1a64d46

rklabs/folly,rklabs/folly,charsyam/folly,facebook/folly,facebook/folly,Orvid/folly,Orvid/folly,floxard/folly,facebook/folly,floxard/folly,Orvid/folly,charsyam/folly,floxard/folly,charsyam/folly,charsyam/folly,facebook/folly,floxard/folly,Orvid/folly,Orvid/folly,rklabs/folly,facebook/folly,floxard/folly,rklabs/folly,rklabs/folly