RND-1267 utils.files.remove: handle mounted files

[tehasdf]

In containerized environments, ismount might return True for files, depending on the filesystem. So yeah, files can be mounted as well.

The listdir call will fail for files though, so this must be actually only done for mounts that are also directory mounts

[tehasdf]

For the 7.0.x branch, this is applied via... sed, in the helm chart, by the hotfix.rnd1267 parameter, introduced in cloudify-cosmo/cloudify-helm#113