adb: libusb: switch from polling for accessibility to a sleep.

For unclear reasons, it seems that for some people, devices are
becoming accessible, inaccessible, and then inaccessible again.
Switch to a sleep for now.

Bug: http://b/62200735
Test: manual
Merged-In: Id51dcb188c3534a57c35cbfd30a181c99115a23c
Change-Id: Id51dcb188c3534a57c35cbfd30a181c99115a23c
(cherry picked from commit 5b8b10e078ef12f21144cdb5fbc932dda47be212)
1 file changed