use remote_user or become_user in docker connection

lib/ansible/plugins/connection/docker.py

@@ -121,8 +121,9 @@ class Connection(ConnectionBase):
         super(Connection, self).exec_command(cmd, in_data=in_data, sudoable=sudoable)
 
         executable = C.DEFAULT_EXECUTABLE.split()[0] if C.DEFAULT_EXECUTABLE else '/bin/sh'
+        exec_user = self._play_context.become_user if self._play_context.become else self._play_context.remote_user
         # -i is needed to keep stdin open which allows pipelining to work
-        local_cmd = [self.docker_cmd, "exec", '-i', self._play_context.remote_addr, executable, '-c', cmd]
+        local_cmd = [self.docker_cmd, "exec", '-u', exec_user, '-i', self._play_context.remote_addr, executable, '-c', cmd]
 
         display.vvv("EXEC %s" % (local_cmd,), host=self._play_context.remote_addr)
         local_cmd = [to_bytes(i, errors='strict') for i in local_cmd]
@@ -169,7 +170,8 @@ class Connection(ConnectionBase):
             # Older docker doesn't have native support for copying files into
             # running containers, so we use docker exec to implement this
             executable = C.DEFAULT_EXECUTABLE.split()[0] if C.DEFAULT_EXECUTABLE else '/bin/sh'
-            args = [self.docker_cmd, "exec", "-i", self._play_context.remote_addr, executable, "-c",
+            exec_user = self._play_context.become_user if self._play_context.become else self._play_context.remote_user
+            args = [self.docker_cmd, "exec", "-u", exec_user, "-i", self._play_context.remote_addr, executable, "-c",
                     "dd of=%s bs=%s" % (out_path, BUFSIZE)]
             args = [to_bytes(i, errors='strict') for i in args]
             with open(to_bytes(in_path, errors='strict'), 'rb') as in_file: