Null pointer exception in FileRotator.java

Sometimes a null pointer exception is thrown when examining files
managed by the file rotator.

The logs from the test show that the Wifi state is changed a large
number of times. On every state change, a write operation is
initiated on the file system. This will eventually result in out
of memory and the call to mBasePath.list() in the maybeRotate(...)
method in FileRotator.java will return null so the iteration will
throw a NullPointerException.

Change-Id: I5d5980d9593bc9ec75281169ca27ee591809903f
add gps gid to system_server

system_server hosts gps service, it should pocess gps
gid, so it can communicate with native gps daemons.

Change-Id: I59d7e99ec996891b19fa15a3ed66e055e6bccad8
Revert "services: don't clear wallpaper when SystemUI"

This reverts commit c7141d24b0156055828787336fe5b953d05c4ef6.