Make end-to-end test clean up after itself, and drop unnecessary use of Docker for it.

tox.ini

@@ -17,12 +17,9 @@ commands =
     black --skip-string-normalization --line-length 100 .
 
 [testenv:end-to-end]
-whitelist_externals = docker
-skip_install = true
-deps =
+deps = -rtest_requirements.txt
 commands =
-    docker build --file tests/end-to-end/Dockerfile --tag borgmatic-test .
-    docker run --rm borgmatic-test py.test tests/end-to-end []
+    py.test tests/end-to-end []
 
 [flake8]
 ignore = E501,W503