[opct][cli] Dedicated mode must be default

The provider cert tool needs to use dedicated mode by default to prevent random cert failures.

It needs to use dedicated by default because there are k8s e2e tests that apply taints to nodes (it is one of the things to test) and if the taints happen to apply to the node where the sonobuoy/plugin Pods are running it will kill the certification process.

If we use dedicated mode, then the taints won't be applied to the dedicated node; the process in which the e2e tests chooses a node works in our favor.

There are 2 requirements for this task:

1. Update tool code so dedicated mode is used by default. Invert the command line options. In other words, default `–dedicated` to true.
2. Update documentation that suggests dedicated mode is optional.