cli/command/swarm: minor cleanups: use Println, rename vars

- use Println to print newline instead of custom format
- use apiClient instead of client for the API client to
  prevent shadowing imports.
- use dockerCLI with Go's standard camelCase casing.
- suppress some errors to make my IDE and linters happier
- fix some tests to work with "go test -update"
- rewrite TestSwarmInit to use sub-tests

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

cli/command/swarm/join_test.go

@@ -23,6 +23,7 @@ func TestSwarmJoinErrors(t *testing.T) {
 	}{
 		{
 			name:          "not-enough-args",
+			args:          []string{},
 			expectedError: "requires 1 argument",
 		},
 		{