EX-9054 lipe: Add SSH stats per agent

EX-9054 lipe: Add SSH stats per agent

- Add stats counters on SSH per agent: error and
  disconnection counters
- Add summary counter on total SSH inactivity
- Disconnect agent when lfs command option request fails
- Report log on INFO level when agent becomes active again
- Fixed minor bugs:
  o memory leak when system error happens in
    pthread_tryjoin_np()
  o Missed stats on job retries

Test-Parameters: trivial testlist=hot-pools
Signed-off-by: Alexandre Ioffe <aioffe@ddn.com>
Change-Id: I35eebf61d35eb913a167ebd795779188a6217dac
Reviewed-on: https://review.whamcloud.com/c/ex/lustre-release/+/53957
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>