Fix override-src-port and override-src-ip flag parsing in register command

[Miles-Garnsey]

Fixes #55

[burmanm]

The bug crept in because there's no tests at all for the command parameters. The least it could do is check all the intended / required parameters, like:

package register

import (
	"testing"

	"github.com/spf13/cobra"
	"github.com/stretchr/testify/require"
	"k8s.io/cli-runtime/pkg/genericiooptions"
)

func TestInputParameters(t *testing.T) {
	require := require.New(t)

	RegisterClusterCmd.RunE = func(cmd *cobra.Command, args []string) error {
		return nil
	}
	cmd := &cobra.Command{
		RunE: func(cmd *cobra.Command, args []string) error {
			return nil
		},
	}
	SetupRegisterClusterCmd(cmd, genericiooptions.NewTestIOStreamsDiscard())
	RegisterClusterCmd.SetArgs([]string{"register", "--source-context", "source", "--dest-context", "dest", "--oride-src-ip", "127.0.0.2"})
	executor := NewRegistrationExecutorFromRegisterClusterCmd(*RegisterClusterCmd)
	require.NoError(RegisterClusterCmd.Execute())
	require.Equal("127.0.0.2", executor.OverrideSourceIP)
}

In this case, you'd notice from Execute() that not all the parameters were correctly named and the test would fail. Later, after fixing the implementation (but not the test) one would notice that the 127.0.0.2 was not parsed correctly. I'm not entirely sure why this implementation doesn't catch the incorrect parameter name itself in Execute() like the other cmds, but this would still catch the implementation issue.

[Miles-Garnsey]

Copying from slack:

--- FAIL: TestInputParameters (0.00s)
    register_test.go:158: 
        	Error Trace:	/Users/milesgarnsey/projects/k8ssandra-client/cmd/kubectl-k8ssandra/register/register_test.go:158
        	Error:      	Received unexpected error:
        	            	unknown command "^TestInputParameters$" for ""
        	Test:       	TestInputParameters
FAIL

I think that what you're seeing is that argument one is picking up the test name, so this isn't going to work. I'm not sure how to work around the way that cobra picks up the first  CLI argument...

If we were going to implement a test like this we'd need to figure out how to work around the way that RegisterClusterCmd.SetArgs([]string{"register", "--source-context", "source", "--dest-context", "dest", "--oride-src-ip", "127.0.0.2"}) seems to pick up the arguments from the test command instead of the ones we want.