Fix deadlock in StagingManager.getSessions() method

When we stage a session we acquire the PackageInstallerSession#mLock
first and then StagingManager#mStagedSessions lock. But in getSessions()
method, we acquire the locks in reverse order which can lead to
deadlock.

Bug: 160113544
Test: atest StagedInstallTest
Change-Id: I7a1abf44db27d4673d43e9b0886610a5bd8b41f6
2 files changed