Only take care of ssh-keys if ensure is set to 'present'

[opteamax]

Trying to remove a user by simply setting "ensure = absent" leads to the following errors:

Error: Cannot create /home/USERNAME/.ssh; parent directory /home/USERNAME does not exist
Error: /Stage[main]/Fcsbase::Install/Accounts::User[USERNAME]/Accounts::Key_management[USERNAME_key_management]/File[/home/USERNAME/.ssh]/ensure: change from absent to directory failed: Cannot create /home/USERNAME/.ssh; parent directory /home/USERNAME does not exist
Notice: /Stage[main]/Fcsbase::Install/Accounts::User[USERNAME]/Accounts::Key_management[USERNAME_key_management]/File[/home/USERNAME/.ssh/authorized_keys]: Dependency File[/home/USERNAME/.ssh] has failures: true
Warning: /Stage[main]/Fcsbase::Install/Accounts::User[USERNAME]/Accounts::Key_management[USERNAME_key_management]/File[/home/USERNAME/.ssh/authorized_keys]: Skipping because of failed dependencies

I added checking ensure == present before instantiation of accounts::key_management to be able to cleanly remove users without warnings and errors.

[Q1tum]

I run into the same problem on FreeBSD, the suggested changes resolve this issue for me.

[pmcmaw]

I have ran this through our internet adhoc pipeline and everything has passed.
The change also looks sane therefore I am going to merge.

Thank you @opteamax for taking the time to submit this PR 👍
We really appreciate it! :-)