EX-3253 iokit: correct device name in ec_using_srv_nid()

EX-3253 iokit: correct device name in ec_using_srv_nid()

Patch changes in ec_using_srv_nid():
- use 'oscname' instead of 'ocsname', that also fixes typo
  introduced by EX-1873
- use explicit --device parameter for echo_client setup, that
  was missed in EX-1873 and completes its work

Test-Parameters: trivial testlist=obdfilter-survey env=ONLY=3a
Fixes: aba6201da5 (EX-1873 iokit: fix the obsolete usage of cfg_device)
Signed-off-by: Mikhail Pershin <mpershin@whamcloud.com>
Change-Id: I661a58299adfba09983ec73f9801726789d79f4a
Reviewed-on: https://review.whamcloud.com/46366
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>