Review connection handling

[dominikl]

The handling of the encrypted/unencrypted connections in the gateway should be reviewed.
See @joshmoore 's comment on #19 (comment) .
With Insight's lock icon open, the unencrypted connection should be used for image import, but blocking port 4063 doesn't trigger an exception as it would be expected, see #19 (comment) . Which indicates that the connection handling / keepalive maybe isn't working as expected.