Scan all init.*.rc files for flash_recovery service.

Clockwork builds may rename init.rc to init.core.rc. Change the OTA
script to scan all init.*.rc files to determine the proper location for
install-recovery.sh.

Bug: 22128990
Change-Id: Icad3497d1663e074b938919b40fc239c84fbeb2b
(cherry picked from commit 610754e5)