merovingian: retrieve cwd for gdk_dbfarm
merovingian: retrieve cwd for gdk_dbfarm

GDK doesn't like a relative dbfarm ("."), so we need to pass an
absolute location to it.  Retrieve it, and give it to sabaoth, which in
turn will give it to mserver in fork_mserver.

This fixes bug #2787

zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb