NetworkManagementService.java: fix error-prone warnings

- Lock objects should be final
- Inner classes should be static if possible

Change-Id: Idca268e03ea1e9f80e64012d1e011dc8bca1d9a8
Merged-In: Idca268e03ea1e9f80e64012d1e011dc8bca1d9a8
Fix: 38446237
Test: Build
1 file changed