http: Rewrite openconnect_obtain_cookie() loop
http: Rewrite openconnect_obtain_cookie() loop

First try XML POST, then fall back to the old method if that breaks.

Signed-off-by: Kevin Cernekee <3105dbb3dd63fbb4f6371cfb04adc6726f76c56b@gmail.com>

atyndall/openconnect,mtmiller/openconnect,brandt/openconnect,neshema/openconnect,neshema/openconnect,don-johnny/openconnect,nmav/openconnect-mine,matlockx/openconnect,brandt/openconnect,neshema/openconnect,cernekee/openconnect,mtmiller/openconnect,nmav/openconnect-mine,matlockx/openconnect,cernekee/openconnect,lins05/openconnect,nmav/openconnect-mine,liiir1985/openconnect,chadcatlett/openconnect,matlockx/openconnect,neshema/openconnect,don-johnny/openconnect,atyndall/openconnect,atyndall/openconnect,brandt/openconnect,chadcatlett/openconnect,mtmiller/openconnect,don-johnny/openconnect,nmav/openconnect-mine,mveplus/openconnect-client,brandt/openconnect,matlockx/openconnect,mveplus/openconnect-client,lins05/openconnect,lins05/openconnect,chadcatlett/openconnect,mveplus/openconnect-client,liiir1985/openconnect,cernekee/openconnect,don-johnny/openconnect,cernekee/openconnect,liiir1985/openconnect,chadcatlett/openconnect,lins05/openconnect,atyndall/openconnect,mveplus/openconnect-client,liiir1985/openconnect,mtmiller/openconnect