Avoid loading app icon bitmap when possible

The layout file is using a CachingIconView for the app icon to avoid
reloading the icon when possible. But, the icon is being explicitly
loaded in MediaDataManager. This change eliminates this unnecessary
work.

Bug: 160591450
Test: manual - heap_profile sysui while toggling play/pause.
Change-Id: I5677e489229fc53f2d5cdc19023acf49a80c7caa