qemuxml2arvtest: Ensure newline at the end of generated .args files
qemuxml2arvtest: Ensure newline at the end of generated .args files

The switch to internal linebreaking of arguments caused a problem when
generating .args files with VIR_TEST_REGENERATE_OUTPUT as the last
argument isn't terminated with a newline.

Switch to using virCommandToStringBuf and append a newline.

Fixes: 0046e0b1c26c8e0167de4a35be2902b9327b0c51
Signed-off-by: Peter Krempa <2cf5c04c61aa466e4a47bfedc747d17279c72ffc@redhat.com>
Reviewed-by: Ján Tomko <4cab11cfb98d3c937327354a78eb07dbb6ee2bc6@redhat.com>

jfehlig/libvirt,zippy2/libvirt,nertpinx/libvirt,olafhering/libvirt,libvirt/libvirt,olafhering/libvirt,zippy2/libvirt,jfehlig/libvirt,crobinso/libvirt,libvirt/libvirt,crobinso/libvirt,crobinso/libvirt,crobinso/libvirt,libvirt/libvirt,nertpinx/libvirt,nertpinx/libvirt,nertpinx/libvirt,jfehlig/libvirt,olafhering/libvirt,jfehlig/libvirt,olafhering/libvirt,libvirt/libvirt,zippy2/libvirt,nertpinx/libvirt,zippy2/libvirt