MRP-1285 at: net AT after connect

once connected, the previously gathered AT statistics is not valid
anymore because may reflect other routing, etc. The connect by itself
could take a long time due to different reasons (e.g. server was not
ready) and net latency got very high (see import_select_connection())
what does not reflect the current situation.

Take into account only the current (re-)CONNECT rpc latency.

Signed-off-by: Vitaly Fertman <vitaly_fertman@xyratex.com>
Change-Id: I8c69de56875c2fe64a5350e055dddd024df9d116
Reviewed-on: http://es-gerrit.xyus.xyratex.com:8080/1603
Tested-by: Jenkins
Reviewed-by: Alexander Boyko <alexander_boyko@xyratex.com>
Reviewed-by: Alexey Lyashkov <alexey_lyashkov@xyratex.com>
Tested-by: Elena Gryaznova <elena_gryaznova@xyratex.com>