use automatic port by default


git-svn-id: https://geuz.org/svn/gmsh/trunk@17570 59c8cabf-10d6-4a28-b43f-3936b85956c4
make onelab work with automatic port id


git-svn-id: https://geuz.org/svn/gmsh/trunk@17571 59c8cabf-10d6-4a28-b43f-3936b85956c4