This commit sets the http handler to the redirect function for let's encrypt
enabled drone instances. In addition, the `Strict-Transport-Security` header is
added to the redirect given `header.Secure` will only be added for gin routes.
This commit resolves#2261.
In our current drone setup, we are not using a proxy, thus letting drone handle
SSL termination. In addition, we are not exposing port 80 (effectively disabling
insecure drone access). When new engineers join and attempt to access drone,
they are not sent a 301 and often complain that they either do not have access
or that drone is broken (when in reality they are just accessing drone via the
incorrect protocol/port).
This commit changes the default behavior when running drone with a server-cert
by only sending redirects on port 80 rather than allowing both secure and
insecure access.
