dashboard: ensure nodeenv downloaded content is owned by current user

dashboard: ensure nodeenv downloaded content is owned by current user

When testing ceph builds in a container we discovered that certain files
could not be deleted by jenkins after a build. This was due to the way
the container maps IDs - files owned by the root user in the container
become owned by the "real" user/jenkins user on the "host".
However, the node tarball that is fetched and unpacked by nodeenv has
a different owner name/uid that is preserved in the tree and this id
gets mapped to something that can be managed by the "fake root" of the
container but not by the "regular" user outside the container.

The simplest workaround I can think of is to chown the tree back
to the current user and avoid leaving files on disk with uncleanly
mapped uids.

Signed-off-by: John Mulligan <jmulligan@redhat.com>