Update comments now that mPackages is no longer a lock

Commit 865fd3a5733 'mPackages is not a lock!' introduced a new object
mLock for locking the package manager, instead of relying on mPackages.
Update the comments to reflect this.

Test: builds
Change-Id: I287d4c8ff22c49a6e0924e4ad4530376e41ef196
1 file changed