adb-remount-test: report wait duration

Report any unusual durations for how long it took to wait for the
device to come back if --print-time flag.  Also report the boot
reason if unexpected.

Test: adb-remount-test.sh
Bug: 132070014
Change-Id: I233bbc7b01b025739d7d63191cb62952fa4b7b2a
1 file changed