test: rename scenario withnetns -> netns

This makes the naming consistent with scenarios added in later
commits.

test/run-tests.sh

@@ -149,7 +149,7 @@ build() {
         buildTest "$@"
     else
         scenario=default buildTest "$@"
-        scenario=withnetns buildTest "$@"
+        scenario=netns buildTest "$@"
     fi
 }
 

test/tests.nix

@@ -22,7 +22,7 @@ import ./make-test.nix rec {
     # needed because duplicity requires 270 MB of free temp space, regardless of backup size.
     virtualisation.diskSize = 1024;
 
-    nix-bitcoin.netns-isolation.enable = (scenario == "withnetns");
+    nix-bitcoin.netns-isolation.enable = (scenario == "netns");
 
     services.bitcoind.extraConfig = mkForce "connect=0";