Exempt apps with INSTALL_PACKAGES from freezer

System applications with INSTALL_PACKAGES permission, like store
apps, have long-running processes in order to keep the system stable
and secure. Don't freeze them even if they are cached.

Bug: 184584402
Test: Verified store apps with the permission won't be frozen.

Change-Id: I4ae45a3688ac6d50c0e7d6ef11ce506b283ee82f
Signed-off-by: Li Li <dualli@google.com>