mds/journal.cc: fix assert in replay()

Fix assert in replay(), check if mds->sessionmap.version is cmapv
instead of assign cmapv to  mds->sessionmap.version. Add missing
second '='.

Signed-off-by: Danny Al-Gaaf <danny.al-gaaf@bisect.de>
Merge pull request #74 from dalgaaf/wip-da-sca-misc

mds/journal.cc: fix assert in replay()

Let's see how many bugs this has been hiding... :)

Reviewed-by: Sage Weil <sage@inktank.com>