deploy: Always use merge commit

I don't recall now the rationale for the previous code; if
we're using this path we always want to be in a container-native
mode.  Currently the "unpack to pure ostree commit" gets triggered
if one uses this on a container image created via raw
`ostree container encapsulate`.

Anyone who wants the prior behavior should instead unencapsulate
and deploy the underlying commit.

lib/src/container/deploy.rs

@@ -81,7 +81,7 @@ pub async fn deploy(
             imp.import(prep).await?
         }
     };
-    let commit = state.get_commit();
+    let commit = state.merge_commit.as_str();
     let origin = glib::KeyFile::new();
     let target_imgref = options.target_imgref.unwrap_or(imgref);
     origin.set_string("origin", ORIGIN_CONTAINER, &target_imgref.to_string());