Omit unsupported media from webonary upload

 * Part of LT-15827.

Change-Id: I4cd3d1b23dffd529f44c7c86f48c524efbda829c
LT-15927: Crash Migrating (incorrect directory)

Copy defaults from the appropriate directory based on what's
being migrated, not which tool the user has open.

Change-Id: I22ed0abef7411f3e7e0f52ad01da2e55dacb9962