Description of problem:{}

The tool tip text associated to "Add additional label" button is confusing. i.e. tool tip says that 

But this is not the case. i.e. user allowed to add additional label if the key is provided with empty values. The node label supported with key and empty value hence this need a correction.

 
How reproducible:
always

Steps to Reproduce:

1. Open OCM UI staging.
2. Open ROSA Classic cluster /OSD wizard.
3. Fill all required fields and reach to machine pool step.
4. Under add node label section, see the tool tip text associated to "Add additional label".
5. Fill the key field and leave value field empty and click "Add additional label"
6. See the behavior.

Actual results:
At step 5, The node label are allowed with a key and without value from Wizard. Node label value is optional but the tool tip suggest that we should enter labels key and values.

Expected results:
Change the tool tip text associated to "Add additional label" to 
"To add an additional label , make sure all of your label's keys are filled out (label's value fields are optional)"