[pm] fix getInstalledApplications

ag/16176950 introduced a regression where duplicated results were
included in getInstalledApplications by mistake because packageState()
might include uninstalled packages. This CL reverts that.

BUG: 208768731
Test: manual and verified that wellbeing doesn't crash
Change-Id: Ica00a47b77d84d9669cc3062332b0d9948ef20e6