init: Move install-recovery.sh back to the standard location

L moved the location of install-recovery.sh from /system/etc/ to
/system/bin. Since CWM recovery isn't looking for this location
anyway, let's return the file to this standard location. This allows
all other code in L to function properly.

Maintain the change to the init to allow flash_recovery to be disabled
in settings.

Change-Id: I8a85db8addeb75a2fd60d809c5ed4edc619ef7ed