Add logging to scale from zero requests
Add logging to scale from zero requests

Trivial change to add logging around scale from zero events in scaling.go.
Previously scale from zero events were not logged in the same way that normal
scaling events are.  This change adds log writes to show when a scale from zero
was requested and when a function successfully moved to > 0 replicas.

Signed-off-by: Richard Gee <320bca71fc381a4a025636043ca86e734e31cf8b@technologee.co.uk>

rgee0/faas,alexellis/faas,rgee0/faas,alexellis/faas,rgee0/faas,rgee0/faas,rgee0/faas,alexellis/faas,rgee0/faas,rgee0/faas,alexellis/faas,alexellis/faas,alexellis/faas,rgee0/faas,rgee0/faas,openfaas/faas,rgee0/faas,openfaas/faas,alexellis/faas,alexellis/faas,openfaas/faas,alexellis/faas