host: Repair MongoDB cluster before the controller
host: Repair MongoDB cluster before the controller

So that it is started with the volume from the previous primary when
rebooting a single node cluster.

Fixes #3847.

Signed-off-by: Lewis Marshall <748e1641a368164906d4a0c0e3965345453dcc93@lmars.net>

flynn/flynn,flynn/flynn,philiplb/flynn,flynn/flynn,philiplb/flynn,philiplb/flynn,lmars/flynn,lmars/flynn,lmars/flynn,lmars/flynn,lmars/flynn,philiplb/flynn,flynn/flynn,philiplb/flynn,flynn/flynn