DO NOT MERGE ANYWHERE: Release mPackages lock earlier

We cannot hold mPackages when calling into generatePackageDexopts().
This method takes Package Manager's mInstallLock. By holding mPackages,
we have lock inversion and hilarity ensues.

Change-Id: Ia11a158677051e3511702f38cde6780e75b256fb
Fixes: 30927731
(cherry picked from commit a8d4f489)