Drop the separate Tor-enabled Debian image.

Just install Tor on the other Debian image and re-use that.

.circleci/Dockerfile.debian

@@ -23,3 +23,8 @@ RUN apt-get --quiet update && \
 COPY . ${BUILD_SRC_ROOT}
 
 RUN "${BUILD_SRC_ROOT}"/.circleci/prepare-image.sh "${WHEELHOUSE_PATH}" "${VIRTUALENV_PATH}" "${BUILD_SRC_ROOT}"
+
+# Only the integration tests currently need this but it doesn't hurt to always
+# have it present and it's simpler than building a whole extra image just for
+# the integration tests.
+RUN ${BUILD_SRC_ROOT}/integration/install-tor.sh

.circleci/Dockerfile.debian-9-tor

@@ -1,3 +0,0 @@
-FROM tahoelafsci/debian:9
-
-RUN ${BUILD_SRC_ROOT}/integration/install-tor.sh

.circleci/config.yml

@@ -166,10 +166,6 @@ jobs:
   integration:
     <<: *DEBIAN
 
-    docker:
-      - image: "tahoelafsci/debian:9-tor"
-        user: "nobody"
-
     environment:
       <<: *UTF_8_ENVIRONMENT
       # Select the integration tests tox environments.
@@ -409,11 +405,3 @@ jobs:
             # Dockerhub web interface) before anything can be pushed to it.
             docker push tahoelafsci/fedora:28
             docker push tahoelafsci/fedora:29
-      - run:
-          name: "Build Tor-enabled image"
-          command: |
-            docker build -t tahoelafsci/debian:9-tor -f ~/project/.circleci/Dockerfile.debian-9-tor ~/project/
-      - run:
-          name: "Push Tor-enabled image"
-          command: |
-            docker push tahoelafsci/debian:9-tor