MINOR: hlua: Fill the request array on the first HTTP applet run

MINOR: hlua: Fill the request array on the first HTTP applet run

When a lua HTTP applet is created, a "request" object is created, filled
with the request information (method, path, headers...), to be able to
easily retrieve these information from the script. However, this was done
when thee appctx was created, retrieving the info from the request channel.

To be ale to update the applet to use its own buffer, it is now performed on
the first applet run. Indead, when the applet is created, the info are not
forwarded yet and should not be accessed. Note that for now, information are
still retrieved from the channel.