Explicitly set the encoding to Fixed, otherwise Cohttp defaults to Chunked

Note that Cohttp leaves the HTTP headers to you, and you'll probably not
realise the default is Chunked and you'll probably not include the correct
transfer encoding header.

Signed-off-by: David Scott <dave.scott@eu.citrix.com>
Don't let the main thread terminate (otherwise the whole app comes crashing down)

Signed-off-by: David Scott <dave.scott@eu.citrix.com>