Get rid of some old serialization workaround code that is not needed because serializer was improved in the meantime. 
Fixing #1254.
Fixed possible race causing corruption of the server savegame.

git-svn-id: https://vcmi.svn.sourceforge.net/svnroot/vcmi/trunk@3339 4dfc6b2a-8b31-0410-aa91-d6c70e3ac834