LU-3143 tests: use facet_active_host to get host

In wait_osc_import_state() called in test_29a of recovery-small,
facet_acitve_host should be used instead of facet_host for the host
could change during failover with FAILURE_MODE=HARD.

Test-Parameters: clientdistro=el6 serverdistro=el6 \
clientarch=x86_64 serverarch=x86_64 clientcount=4 \
osscount=2 mdscount=2 austeroptions=-R failover=true \
useiscsi=true testlist=recovery-small

Signed-off-by: Hongchao Zhang <hongchao.zhang@intel.com>
Signed-off-by: Jian Yu <jian.yu@intel.com>
Change-Id: I7fe45c7d979b64d802894c92eaad6f76bec3fadf
Reviewed-on: http://review.whamcloud.com/6036
Tested-by: Hudson
Reviewed-by: Niu Yawei <yawei.niu@intel.com>
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>