[libvirt] [PATCH]: don't hardcode default port 22 for ssh protocol

Hi, attached patch removes the hardcoded port 22 when going through ssh, ssh uses it by default. This makes it easier to override this via .ssh/config on a per host basis instead of having to add this to the connection URI explicitly. While at that I cleaned up some free vs. VIR_FREE usage and replaced pointer intializations with 0 by NULL. Cheers, -- Guido P.S.: this originated from Debian Bug #513605