build: fix "missing initializer" errors in virsh.c

build: fix "missing initializer" errors in virsh.c

Found when attempting to build on Fedora 17 alpha with:

   ./autogen.sh --system --enable-compile-warnings=error

(this same build command works without problem on Fedora 16). All
other struct initializers for this struct have the extra field filled
in (almost always to 0), so the two errant ones were fixed by adding
in the extra 0 field.