socks.c: fix check on get_user_pass() return value(s)

socks.c: fix check on get_user_pass() return value(s)

My compiler rightfully complains that the checks on creds.username and
creds.password always evaluate to true, so remove those checks.

Judging from the code, they were meant to check the returned values by
get_user_pass().  So instead of these non-functioning checks, just check
the return value of get_user_pass().

Signed-off-by: Steffan Karger <steffan@karger.me>
Acked-by: Gert Doering <gert@greenie.muc.de>
Message-Id: <1452701348-9577-1-git-send-email-steffan@karger.me>
URL: http://article.gmane.org/gmane.network.openvpn.devel/10993
Signed-off-by: Gert Doering <gert@greenie.muc.de>