s/memoryswap/memswap/

Since clearly the equivalent of 'memory' is 'memswap' grumble

repo2docker/buildpacks/base.py

@@ -392,7 +392,7 @@ class BuildPack(LoggingConfigurable):
         limits = {
             # Always disable memory swap for building, since mostly
             # nothing good can come of that.
-            'memoryswap': -1
+            'memswap': -1
         }
         if memory_limit:
             limits['memory'] = memory_limit

repo2docker/buildpacks/docker.py

@@ -22,7 +22,7 @@ class DockerBuildPack(BuildPack):
         limits = {
             # Always disable memory swap for building, since mostly
             # nothing good can come of that.
-            'memoryswap': -1
+            'memswap': -1
         }
         if memory_limit:
             limits['memory'] = memory_limit