Wojciech Lis <wlis@fb.com> [Mon, 11 Dec 2017 16:51:13 -0800] rev 35426
workers: don't use backgroundfilecloser in threads
This disables background file closing when in not in main thread
Test Plan:
Ran pull, update, sparse commands and watched the closer threads created and destroyed in procexp.exe
ran test on CentOS. No tests broken compared to the base
Differential Revision: https://phab.mercurial-scm.org/D1457