LU-11213 uapi: Remove unused CONNECT flag

LU-11213 uapi: Remove unused CONNECT flag

The plain layout connect flag was added as part of an
earlier implementation of LU-11213, but the design was
improved before landing and the flag was not needed.

Let's remove it.  Since it was never actually marked as
supported in any client/server version, we can just remove
it entirely, leaving the flag bit open for future use.

Signed-off-by: Patrick Farrell <pfarrell@whamcloud.com>
Change-Id: I30946a50299268d00cbfee2081607effd0e4fb47
Reviewed-on: https://review.whamcloud.com/36008
Reviewed-by: Shilong Wang <wshilong@ddn.com>
Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: Lai Siyao <lai.siyao@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>