httpauth: Add space after commas in HTTP/RTSP auth header

This fixes access to Grandstream cameras, which return 401 otherwise.
VLC sends Authorization: header with spaces between parameters, and it
is known to work with Grandstream devices and broad range of other HTTP
and RTSP servers, so author considers switching to such behaviour safe.

See RFC 2617 (HTTP Auth).

Signed-off-by: Luca Barbato <lu_zero@gentoo.org>
