adbd: wait for FUNCTIONFS_BIND for up to a second, then retry.

Occasionally, after we open the functionfs endpoint and write our
descriptors to it, we end up in a state where we never receive any
events from ep0, presumably due to a race against some other part of
the system, since adding sleeps reduces the likelihood. Add an
(arbitrarily chosen) timeout for the initial FUNCTIONFS_BIND we read,
and retry on failure.

Bug: http://b/128679787
Test: unplug and replug a blueline 14,000 times with a usb switch board
Change-Id: I4b3d5d552179ee7f3fefcc15f9575f793926f784