MPD redirect handling broken
Created by: davemevans
#482 was regressed by #1215. This can be tested using http://rdmedia.bbc.co.uk/dash/ondemand/testcard/1/deadend/client_manifest-nosurround-ctv-relative.mpd
This also had the side effect of breaking resolution of relative MPD URLs as reported by @lightsedge in https://github.com/Dash-Industry-Forum/dash.js/issues/1321#issuecomment-208729883.
PR to be submitted shortly.