Check manifest if runtime state of app is DEFAULT

Before we were considering that the app was enabled in this case, which
might not be always true.

Bug: 80227098
Test: atest AppBackupUtilsTest
Test: Check app w/ manifest enabled="true" is backed-up, but
      enabled="false" is not.

Change-Id: I4625aa39ba0de45ce6689f2375245081a5d4d722