Include env variables defined in a dependency in the step itself.

Prior to this commit, a `dependency` defined by the `molecule.yaml` file
would not honor the values in its `env` map. Consider the following:

```yaml
dependency:
  name: shell
  command: env
  env:
    FOO: bar
```

Invoking `molecule test` would show that `FOO` is not set during the run
of this dependency. The cause was the fact that these values were never
actually passed to the `util.run_command()` invocation. This also means
`MOLECULE_EPHEMERAL_DIRECTORY` and similar `MOLECULE_*` environment
variables that are defined by the dependency's `default_env` property
were also never available to the dependency's environment.

src/molecule/dependency/base.py

@@ -54,7 +54,7 @@ def execute_with_retries(self):
         exception = None
 
         try:
-            util.run_command(self._sh_command, debug=self._config.debug, check=True)
+            util.run_command(self._sh_command, debug=self._config.debug, check=True, env=self.env)
             msg = "Dependency completed successfully."
             LOG.info(msg)
             return
@@ -71,7 +71,7 @@ def execute_with_retries(self):
             self.SLEEP += self.BACKOFF
 
             try:
-                util.run_command(self._sh_command, debug=self._config.debug, check=True)
+                util.run_command(self._sh_command, debug=self._config.debug, check=True, env=self.env)
                 msg = "Dependency completed successfully."
                 LOG.info(msg)
                 return