LU-17312 tests: skip conf-sanity test_53 in interop

LU-17312 tests: skip conf-sanity test_53 in interop

Skip conf-sanity test_53 in interop because older servers cannot
stop any running service threads above threads_max.

Remove old test interop for servers < 2.3.

Test-Parameters: trivial testlist=conf-sanity
Test-Parameters: testlist=conf-sanity env=ONLY=53 serverversion=2.12
Fixes: 183cb1e3cd ("LU-947 ptlrpc: allow stopping threads above threads_max")
Signed-off-by: Andreas Dilger <adilger@whamcloud.com>
Change-Id: Ia95405060c607c7a070720ed32a7a43b1c3ebbe5