Expand access to gatekeeperd.

This enables access to gatekeeperd for anybody who invokes Android
framework APIs. This is necessary because the AndroidKeyStore
abstraction offered by the framework API occasionally communicates
with gatekeeperd from the calling process.

Bug: 20526234
Change-Id: I3362ba07d1a7e5f1c47fe7e9ba6aec5ac3fec747