b=1541: fix LASSERT on mismatched transnos during open-unlink testing

b=1541: fix LASSERT on mismatched transnos during open-unlink testing
r=phik

- the open request now keeps a pair of pointers in its replay data:
  - the och that has always been there for fixing up open filehandles
  - the close request that has been created to balance it, which may or may
    not have made it over the wire yet, for fixing up the filehandle cookie it
    sends to the MDS

- the explicit updating of the close req replaces the previous walking of the
  sending list, which was both insufficient _and_ excessive

- suppress the "asked for EA, got none" message in the case of a 0-nlink file

- when processing an INTENT_ONLY enqueue request, return a successful 0 rather
  than ELDLM_LOCK_ABORTED, which only confused the clients

- when opening by FID, be sure to set the intent disposition flags
  appropriately

- triple the timeout, instead of doubling it, for the replay-completed PING, to
  better suit the numerology of the pinger and timeout values