edify: update the RunBackup function

set_perm was removed a few days ago, use the built in function for setting permissions
TMPFS does not have xattr set, which is across most devices. dump the scripts into system so set_metadata will work

Change-Id: I9ee00f15fa0be1eef31c5435b9d94845fd3aa630

Conflicts:
	tools/releasetools/edify_generator.py