tests: mock execv/execve
tests: mock execv/execve

Learn to override the paths to the program to execute (vhost-user
helpers are executed to check for runtime capabilities).

Signed-off-by: Marc-André Lureau <a6f2b960a4aca61381fc650a67901b2ac8e83e6d@redhat.com>
Reviewed-by: Cole Robinson <7cd45ff6ad1fb7cf556a02797d774247851499f8@redhat.com>

libvirt/libvirt,andreabolognani/libvirt,jardasgit/libvirt,andreabolognani/libvirt,olafhering/libvirt,olafhering/libvirt,zippy2/libvirt,crobinso/libvirt,olafhering/libvirt,libvirt/libvirt,andreabolognani/libvirt,nertpinx/libvirt,crobinso/libvirt,libvirt/libvirt,nertpinx/libvirt,nertpinx/libvirt,zippy2/libvirt,nertpinx/libvirt,zippy2/libvirt,jardasgit/libvirt,olafhering/libvirt,jfehlig/libvirt,libvirt/libvirt,jardasgit/libvirt,andreabolognani/libvirt,fabianfreyer/libvirt,fabianfreyer/libvirt,fabianfreyer/libvirt,crobinso/libvirt,jfehlig/libvirt,nertpinx/libvirt,jfehlig/libvirt,jfehlig/libvirt,crobinso/libvirt,fabianfreyer/libvirt,fabianfreyer/libvirt,zippy2/libvirt,jardasgit/libvirt,jardasgit/libvirt,andreabolognani/libvirt