adb: fix IOKit handle leaks on OS X.

Bug: https://code.google.com/p/android/issues/detail?id=219085
Test: Removed sleep in RunLoopThread, compared before/after this patch

Bug: http://b/33283523
(cherry picked from commit b6a2f595151dc6de850f7bc0e2aa5aec3db80213)
Change-Id: Ia65bbedfb7d47bdb02bdfb69778784e5e855900b
1 file changed