test/mon/*: prime mon with initial command before injection

test/mon/*: prime mon with initial command before injection

The osdmonitor_prepare_command is very fragile.  Send an initial command
to the mon beforehand.  This seems to prevent the initial command from
getting combined into an early mon proposal with some other stuff.

Alternatively, we could remove these tests and this mechanism entirely as
it is likely to great in the future when the next set of mon changes are
made, but they have shown themselves to be useful it catching other
regressions, so we'll patch them up for a bit longer.

Signed-off-by: Sage Weil <sage@redhat.com>