Link to HTTPS URLs in engine comments

Updates most of the instances of HTTP urls in the engine's
comments. Does not account for any use in the code itself,
documentation, contrib, or project files.

Signed-off-by: Eric Windisch <eric@windisch.us>

integration-cli/docker_cli_proxy_test.go

@@ -21,7 +21,7 @@ func TestCliProxyDisableProxyUnixSock(t *testing.T) {
 }
 
 // Can't use localhost here since go has a special case to not use proxy if connecting to localhost
-// See http://golang.org/pkg/net/http/#ProxyFromEnvironment
+// See https://golang.org/pkg/net/http/#ProxyFromEnvironment
 func TestCliProxyProxyTCPSock(t *testing.T) {
 	testRequires(t, SameHostDaemon)
 	// get the IP to use to connect since we can't use localhost