Start uevent handling thread early

This change starts uevent handling thread before EvsEnumerator is
being instantiated to avoid a problematic scenario that a device
addition happens between EvsEnumerator object creation and it start
listening uevents.

Bug: 133156438
Test: Test with EVS on Hawk
Change-Id: Id264bb1674ded83b143d659de47b9190a118c673
Signed-off-by: Changyeon Jo <changyeon@google.com>
3 files changed