m4/virt-lib: move LIBVIRT_ARG_WITH out of LIBVIRT_CHECK_(LIB|LIB_ALT|PKG)

m4/virt-lib: move LIBVIRT_ARG_WITH out of LIBVIRT_CHECK_(LIB|LIB_ALT|PKG)

Following patch will update LIBVIRT_CHECK_(LIB|LIB_ALT|PKG) macros in
a way that you will be able to call a another macro as a fallback if
the first one fails.  To allow that, we need to move the
LIBVIRT_ARG_WITH out of those macro to not have two or more same lines
in output of "configure --help".

Signed-off-by: Pavel Hrdina <phrdina@redhat.com>