Add docker.socket requirement for docker.service

Without this the docker.socket would not start by default when starting
the docker.service leading to failures to start.

Signed-off-by: Eli Uriegas <eli.uriegas@docker.com>
(cherry picked from commit 88885d18b1bb0ef91eab4ad3311773f9c40838b7)
Signed-off-by: Andrew Hsu <andrewhsu@docker.com>
Upstream-commit: 93f125a2602b7eb72128cbc16d9d35c9d92ed18a
Component: packaging

components/packaging/systemd/docker.service

@@ -4,6 +4,7 @@ Documentation=https://docs.docker.com
 BindsTo=containerd.service
 After=network-online.target firewalld.service
 Wants=network-online.target
+Requires=docker.socket
 
 [Service]
 Type=notify