init: fix expand environment

Change-Id: Idbb8bbc89fff3de50bb75974b9fe847011e67395
mkbootimg: fix sign error comparison

Change-Id: I37aa465cde6cce9b70d9e018a0cf4a1c6cf5f3c0
Merge changes I37aa465c,Idbb8bbc8 into android-5.0

* changes:
  mkbootimg: fix sign error comparison
  init: fix expand environment