If docker-puppet.py (or container-puppet.py) is run under docker prior
to the facter config being generated, the file is created as a
directory. This causes a failure later when we try to write the file
out.
Change-Id: I9b5a1e06e73b3b4cfc0ebfaeba8f1eb4b5d6fcfe
Closes-Bug: #1852606
(cherry picked from commit 3e25c2c48308694bbae737ad7699fe540ed1a098)