D-Bus: Fix use of Bus.get_proxy outside async methods
D-Bus: Fix use of Bus.get_proxy outside async methods

Fixes bug 644275.

kamanashisroy/aroop,frida/vala,rvu95/vala,Distrotech/vala,playya/vala,frida/vala,Distrotech/vala,rvu95/vala,GNOME/vala,tjol/vala-tjol,playya/vala,kamanashisroy/aroop,rvu95/vala,flobrosch/vala-fixes,severinh/vala,GNOME/vala,kamanashisroy/aroop,flobrosch/vala-fixes,tjol/vala-tjol,GNOME/vala,frida/vala,playya/vala,Distrotech/vala,jessevdk/vala,jessevdk/vala,severinh/vala,spidermonkdust/vala,GNOME/vala,spidermonkdust/vala,jessevdk/vala,frida/vala,frida/vala,xdave/pvala,flobrosch/vala-fixes,tjol/vala-tjol,severinh/vala,spidermonkdust/vala