Wait for IDLE state before mounting on insert

As soon as we recive the insert event we try to
mount the mmc sending a "volume mount" command.
But, the volume manager sometimes is still on
"pending" state, and the insertion mount will
fail.

This patch calls the doMount command on insert
only after the state has changed to idle.
This way, the mount will not fail, because the
state is pending.

Change-Id: I1f8f13c8e232a6b9159eeb78a9484838f1c600af
Signed-off-by: Axel Haslam <axelhaslam@ti.com>