tests: Add cli.Context helper functions

Created two new helper functions to create a `cli.Context` with and without a
`cli.App`.

Calling these functions simplifies a lot of test code.

Signed-off-by: James O. D. Hunt <james.o.hunt@intel.com>

cli/spec_test.go

@@ -21,7 +21,7 @@ func TestSpecCliAction(t *testing.T) {
 	assert.True(ok)
 
 	flagSet := flag.NewFlagSet("flag", flag.ContinueOnError)
-	ctx := cli.NewContext(&cli.App{}, flagSet, nil)
+	ctx := createCLIContext(flagSet)
 	defer os.Remove(specConfig)
 	err := actionFunc(ctx)
 	assert.NoError(err)