Always execute actions on the runQueue

A View that is not attached will place posted actions on the
ViewRoot's runQueue. Previously, this runQueue was only ever executed
during a layout (during performTraversals()). This works in most situations
(a View that is added to or removed from the hierarchy will force a layout
in general), but not in all cases. For example, a new View being added to
a ListView will not cause a layout, so any actions posted to that View
prior to its being attached will not be run until some indeterminate time
later when a layout happens to run.

The fix is to execute the (typically empty) runQueue on every traversal.

Issue #6366678 View.post() ignored when called on an unattached ListView item

Change-Id: I94e6fdd9da6bb57fd83b547f8d742cd0ddfecbd6