LU-11206 tests: Use import_ready to check IDLE

LU-11206 tests: Use import_ready to check IDLE

When checking if a client/OST import is up, we have to
check for IDLE as well as FULL.

wait_osc_import_ready is provided for this, but a few spots
don't use it, so they occasionally fail.

Signed-off-by: Patrick Farrell <pfarrell@whamcloud.com>
Change-Id: I826659a7f5953dee4e4551c1177479ef742b5589
Reviewed-on: https://review.whamcloud.com/34225
Reviewed-by: Alex Zhuravlev <bzzz@whamcloud.com>
Reviewed-by: James Nunez <jnunez@whamcloud.com>
Tested-by: Jenkins
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>