If Config.GetEnv was called when envDeps was uninitialized (for
example in a test) it would panic, which if recovered (for example in
a test) would cause it to continue without unlocking the mutex, and
could later deadlock. Fix the initialization by initializing in
GetEnv if necessary, and use defer to avoid holding the mutex after
a panic.
Test: soong tests
Change-Id: I453522faaf47ff6fbc4702345cfe177100bdc522