LU-1943 ofd: save server last transaction number

LU-1943 ofd: save server last transaction number

After reading server data from the last_rcvd file we must store the
last transaction number in lu_target.  Otherwise we write a zero last
transaction number back to last_rcvd, causing transaction numbers to
roll back to 2^32 every time the server is restarted.  This can lead
to 'server went back in time' client console errors.

Whamcloud-bug-id: ORI-670
Signed-off-by: Ned Bass <bass6@llnl.gov>
Signed-off-by: Mikhail Pershin <tappro@whamcloud.com>
Change-Id: Iaff4af3e4bd6fce0da1d1b0886147538c3300c1e
Reviewed-on: http://review.whamcloud.com/4190
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Ian Colle <Ian.Colle@intel.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>