Fix a bug that would access uninitialized data.

Fix a bug where mThread is initialized before mRequests, causing
the new thread to access uninitialized mRequests.

Test: None. This is a race condition depending on when the thread is
started and hard to reproduce.
Bug: 231647009

Change-Id: I68037125bf4d14846585bd3a038844e4a7ced377
(cherry picked from commit 5e26ad3b)