RKE2 extraMounts still can't be used

[hardys]

What happened:
#476 was closed via #504 but AFAICS the configuration format is still incorrect and thus extraMounts still can't be used.

What did you expect to happen:

According to the RKE2 docs, the expected format is:

kube-apiserver-extra-mount: 
   - "/tmp/foo:/root/foo"

When passing a config like:

serverConfig:
    kubeAPIServer:
      extraMounts:
        "/tmp": "/mnt/tmp"

Prior to #504 we saw a format like:

kube-apiserver-extra-mount:
  /tmp: /mnt/tmp

However since the fix we see a format like:

kube-apiserver-extra-mount:
- /tmp=/mnt/tmp

How to reproduce it:

Deploy with a config that specifies extraMounts similar to the serverConfig mentioned above.

Anything else you would like to add:
AFAICS the problem is we use the componentMapToSlice function which is designed to format for environment variables.

Also note we use the same function in the tests, which is probably unwise since we're not actually testing for the expected format.

[hardys]

/cc @alexander-demicev

[alexander-demicev]

@hardys would you be able to test the fix #544?