Skip sending user home when the overview command queue is pending.

Tapping the overview scrim during an app -> overview transition in 3-button nav can replace that state transition's aniamtion, leaving the device in a broken state. The assumption is that the user did not mean to tap the scrim while quickly tapping the overview button. Skipping the startHome request if the overview command queue is not empty.

Flag: not needed
Fixes: 284920213
Test: quickly tapped overview button and quickly tapped scrim; added logs to check error case
Change-Id: I8fea76d810e550e28a61a4528796b358103cb5b3