ORNL-28 recovery: rework extend_recovery_timer()

ORNL-28 recovery: rework extend_recovery_timer()

extend_recovery_timer() is used to adjust timeout value of a recovering
target. In the original implementation, there was a problem it stopped
the target from firing a timer again for version recovery case.

Change-Id: I815a15fb5d3104e52a189eed1529c58d7a8d03b9
Signed-off-by: Jinshan Xiong <jay@whamcloud.com>
Reviewed-on: http://review.whamcloud.com/1620
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Mikhail Pershin <tappro@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>