uclient-http: fix seq field check to use correct field

uclient-http: fix seq field check to use correct field

The code was checking uh->uc.seq for changes to detect redirects, but
only uh->seq is actually incremented (in uclient_http_init_request and
uclient_http_reset_state). This meant the redirect detection check was
always comparing against an unchanging value.

Signed-off-by: Felix Fietkau <nbd@nbd.name>