gio-tool: Fix memory leaks on error paths in mount command
gio-tool: Fix memory leaks on error paths in mount command

Various GErrors were being leaked.

Coverity CID: 1357351 (amongst others)

johne53/MB3Glib,endlessm/glib,johne53/MB3Glib,johne53/MB3Glib,endlessm/glib,johne53/MB3Glib,johne53/MB3Glib,endlessm/glib,endlessm/glib,endlessm/glib,johne53/MB3Glib