fix: don't automatically use GRE mesh when bridge name isn't phenix

Commit 7b80f40 incorrectly assumed users would always want to use the
GRE mesh namespace bridge capability in minimega when the default bridge
for an experiment was not `phenix` (the default).

docker/Dockerfile.minimega

@@ -3,7 +3,7 @@
 ARG  MM_REV
 FROM ghcr.io/activeshadow/minimega/minimega:${MM_REV}
 
-ARG   MINIMEGA_REVISION
+ARG   MM_REV
 LABEL org.opencontainers.image.base.name="ghcr.io/activeshadow/minimega/minimega:${MM_REV}"
 ARG   PHENIX_REVISION=local-dev
 LABEL gov.sandia.phenix.revision="${PHENIX_REVISION}"

src/go/api/experiment/experiment.go

@@ -557,7 +557,7 @@ func Start(ctx context.Context, opts ...StartOption) error {
 		// them. This cannot be done as part of the minimega script template since
 		// the VM taps (and thus bridges) do not get created until the overall
 		// minimega namespace is launched.
-		if exp.Spec.UseGREMesh() || exp.Spec.DefaultBridge() != "phenix" {
+		if exp.Spec.UseGREMesh() {
 			if err := mm.CreateBridge(mm.NS(exp.Metadata.Name), mm.Bridge(exp.Spec.DefaultBridge())); err != nil {
 				if !o.mmErrAsWarn {
 					mm.ClearNamespace(exp.Spec.ExperimentName())