Append idempotence callback plugin path
Append idempotence callback plugin path

During the idempotence test, the path of the idempotence plugin,
provided by molecule is appended to the existing one, if any, instead of
overwriting it.

metacloud/molecule,metacloud/molecule,cimarron-pistoncloud/molecule,metacloud/molecule,rgreinho/molecule,j0lly/molecule,j0lly/molecule,cimarron-pistoncloud/molecule,rjfellman/molecule,rgreinho/molecule,kharkevich/molecule,retr0h/molecule,kireledan/molecule,rjfellman/molecule,j0lly/molecule,cimarron-pistoncloud/molecule,rgreinho/molecule,rjfellman/molecule,retr0h/maquina