LU-12378 ptlrpc: always reset generation for idle reconnect

LU-12378 ptlrpc: always reset generation for idle reconnect

Idle reconnetion is common case and reconnections will
be quick mostly, so always reset generation for this case,
otherwise, it will make application fail just for Idle
reconnection feature.

Change-Id: Ia1531df6a3288663d832865e48a30b448b225766
Signed-off-by: Wang Shilong <wshilong@ddn.com>
Reviewed-on: https://review.whamcloud.com/35052
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Alex Zhuravlev <bzzz@whamcloud.com>
Reviewed-by: Li Xi <lixi@ddn.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>