Fix underlinking of libvirt_driver_interface.so

Always add udev linker flags when WITH_UDEV is enabled to avoid
underlinking.

See commit 43dbcb15 (interface: always build all available backends)
Signed-off-by: NNatanael Copa <ncopa@alpinelinux.org>

src/Makefile.am

@@ -1457,12 +1457,11 @@ libvirt_driver_interface_la_LIBADD =
 if WITH_NETCF
 libvirt_driver_interface_la_CFLAGS += $(NETCF_CFLAGS)
 libvirt_driver_interface_la_LIBADD += $(NETCF_LIBS)
-else ! WITH_NETCF
+endif WITH_NETCF
 if WITH_UDEV
 libvirt_driver_interface_la_CFLAGS += $(UDEV_CFLAGS)
 libvirt_driver_interface_la_LIBADD += $(UDEV_LIBS)
 endif WITH_UDEV
-endif ! WITH_NETCF
 if WITH_DRIVER_MODULES
 libvirt_driver_interface_la_LIBADD += ../gnulib/lib/libgnu.la
 libvirt_driver_interface_la_LDFLAGS += -module -avoid-version