Detect when a sandbox was created for an already configured package.
Detect when a sandbox was created for an already configured package.

In this case we need to reconfigure immediately, skipping reinstallation of
add-source deps.

Fixes #1349.

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