GpuService: secure setUpdatableDriverPath

setUpdatableDriverPath should only be called by system_server and
developer driver path needs to be protected by a lock.

Bug: 162383705
Bug: 159240322
Test: ./gapit validate_gpu_profiling --os android
Change-Id: I48896325598acab89079dbc658ddf9b92d303244
Merged-In: I48896325598acab89079dbc658ddf9b92d303244