LU-10650 obd: add check to obd_statfs

LU-10650 obd: add check to obd_statfs

The race could happend between mount and lctl get_param.
Because procfs files are ready before a full obd initialization.
For example:
3372:0:(dt_object.h:2509:dt_statfs()) ASSERTION( dev )
3372:0:(dt_object.h:2509:dt_statfs()) LBUG
Pid: 3372, comm: lctl
Call Trace:
	libcfs_call_trace+0x4e/0x60[libcfs]
	lbug_with_loc+0x4c/0xb0[libcfs]
	tgt_statfs_internal+0x2ea/0x350[ptlrpc]
	ofd_statfs+0x66/0x470 [ofd]
	lprocfs_filesfree_seq_show+0xf6/0x520 [obdclass]
	ofd_filesfree_seq_show+0x12/0x20 [ofd]

The patch adds a check of completed obd_setup to obd_statfs().
The patch adds the sanity 276 test.

Lustre-change: https://review.whamcloud.com/31243
Lustre-commit: 4f40429775c49468d9ec1fec34d5e7500ac01116

Signed-off-by: Alexander Boyko <c17825@cray.com>
Cray-bug-id: LUS-2665
Change-Id: I55a9ffa7e036f486388a8f548051d28974d47951
Reviewed-by: Alexey Lyashkov <c17817@cray.com>
Reviewed-by: Andriy Skulysh <c17819@cray.com>
Signed-off-by: Minh Diep <minh.diep@intel.com>
Reviewed-on: https://review.whamcloud.com/31752
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: John L. Hammond <john.hammond@intel.com>