Don't call into pkg mgr svc w/ lock held

In general, there's no reason to hold the lock when calling into external
components. However, in practice, this can deadlock. When dumping its
state, Package Manager Service holds a lock while it calls into other
packages to dump their state. These other packages (such as Package
Installer Session) typically take their own lock to dump coherent state.
And, thus, a deadlock.

Bug: 30419998
Change-Id: I0807b8742316d084e381be8721d1b3d41143b82c