LU-11623 tests: Fix sanity 27E to ensure getattr RPC

LU-11623 tests: Fix sanity 27E to ensure getattr RPC

While cat does perform fstat() on the file it opens,
I guess it's not guaranteed.
More importantly, we really need to ensure the locks
that the file has after creation are dropped before
we issue our stat() to ensure the RPC is actually made,
since it's this GETATTR RPC that is ensuring easize
update from MDT response.

Change-Id: Ic86229ac514e1385c665c6c0d9f6eef13d9748f5
Signed-off-by: Oleg Drokin <green@whamcloud.com>
Test-Parameters: trivial
Reviewed-on: https://review.whamcloud.com/35067
Tested-by: Jenkins
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Patrick Farrell <pfarrell@whamcloud.com>
Reviewed-by: James Nunez <jnunez@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>