Fix init order problem between PackageManagerService and ArtManagerLocal.

PackageManagerService calls initSystemApps in its constructor, which
may try to call ArtManagerLocal.clearAppProfiles, but ArtManagerLocal
hasn't yet been registered at that point (it depends on PMS).

Work around the problem by skipping the clearing of profiles in that
case, since both ART Service and the ART runtime ignore invalid
profiles.

Test: atest apex_apkinapex_tests
  with dalvik.vm.useartservice=true
Bug: 273923424
Change-Id: I8571c960b78cff3622f8bd5d05cd2ed8b9b6f4f1