[automerger skipped] Merge "Detach pollThread only if it is joinable" into pie-vts-dev am: cf4a2880c9
am: 7a2b3edec5 -s ours
am skip reason: SHA1 7a2b3edec5 skipped by user wyau

Change-Id: I7462da6f078837df605af65367b2139b038eb806