Fixing issue with PiP aspect ratio being clobbered.

- We should only initialize the initial aspect ratio to the default
  aspect ratio once, instead of when the resources are reloaded.
  Otherwise, they will be clobbered when the configuration changes.
  This is a regression from ag/2295004.

Bug: 62702553
Test: Set PiP aspect ratio from landscape-locked activity, ensure that
      it stays in that aspect ratio after the pip menu dismisses.

Change-Id: Id82f9081c25c7d6482cf7bcf0268fedb9068eabe