Fix incorrect locking order

PackageManagerService should not call into
DevicePolicyManagerService with a lock held.
Lock only the necessary parts of the code so
that we're not holding a lock when calling into
DPMS.

Change-Id: I6d9ae02dc82a39123948cb826d97654fb44ba58b
Fixes: 119804954
Test: atest GtsSuspendAppsTestCases