Make test suite network dependencies more robust

cabal-install/cabal-install.cabal

@@ -176,15 +176,12 @@ Test-Suite unit-tests
         Cabal,
         containers,
         mtl,
-        network,
         pretty,
         process,
         directory,
         filepath,
         stm,
         time,
-        network,
-        network-uri,
         HTTP,
         zlib,
 
@@ -197,6 +194,11 @@ Test-Suite unit-tests
   if flag(old-directory)
     build-depends: old-time
 
+  if flag(network-uri)
+    build-depends: network-uri >= 2.6, network >= 2.6
+  else
+    build-depends: network-uri < 2.6, network < 2.6
+
   if os(windows)
     build-depends: Win32
     cpp-options: -DWIN32