So we don't need to call VersionedPackage#getPackageName and
VersionedPackage#getVersionCode to compare 2 VersionedPackages.
Note you must also override #hashCode whenever you override #equals.
Bug: 147028082
Test: atest StagedRollbackTest
Change-Id: Ib1fac7e0521e2ccde0c2bb1f3fd28c0a7cd70234