Fix the haddock --html-location= for relative URLs
Fix the haddock --html-location= for relative URLs

The previous fix in isue #1407 turned out to be in the wrong place and
so applied to both the haddock-html from the ghc-pkg output, and also to
the location passed via the --html-location flag. For the
--html-location flag it is important that we can use relative URLs like
/package/$pkg-$version/docs because that is what we need for hackage.
Note that that is a relative URL, it's relative to the server root.
However that was being interpreted as a local file path and being given
the file:// prefix. So now we move the file:// URL stuff to the right
place so it only applies to the location given in the haddock-html field
of the package registration.

beni55/cabal,rimmington/cabal,valderman/cabal,ghc-android/cabal,edsko/cabal,lukexi/cabal,themoritz/cabal,fugyk/cabal,Peaker/cabal,garetxe/cabal,fpco/cabal,randen/cabal,anton-dessiatov/cabal,kolmodin/cabal,eric-stanley/cabal,randen/cabal,headprogrammingczar/cabal,seereason/cabal,rimmington/cabal,typelead/epm,christiaanb/cabal,mydaum/cabal,mightybyte/cabal,ian-ross/cabal,x-y-z/cabal,eric-stanley/cabal,x-y-z/cabal,typelead/epm,gbaz/cabal,lukexi/cabal,gridaphobe/cabal,gbaz/cabal,kolmodin/cabal,headprogrammingczar/cabal,thoughtpolice/cabal,plow-technologies/cabal,trskop/cabal,sopvop/cabal,trskop/cabal,valderman/cabal,seereason/cabal,mightybyte/cabal,corngood/cabal,mmakowski/cabal,ian-ross/cabal,Helkafen/cabal,kosmikus/cabal,mmakowski/cabal,plumlife/cabal,bennofs/cabal,gridaphobe/cabal,ghc-android/cabal,corngood/cabal,plow-technologies/cabal,sopvop/cabal,fugyk/cabal,mydaum/cabal,Helkafen/cabal,thoughtpolice/cabal,triplepointfive/cabal,sopvop/cabal,martinvlk/cabal,christiaanb/cabal,kosmikus/cabal,anton-dessiatov/cabal,themoritz/cabal,fpco/cabal,plumlife/cabal,thomie/cabal,beni55/cabal,themoritz/cabal,Heather/cabal,triplepointfive/cabal,bennofs/cabal,thomie/cabal,Peaker/cabal,martinvlk/cabal,enolan/cabal,garetxe/cabal,enolan/cabal,Heather/cabal,edsko/cabal