Test different regenerate values with nonexistent keys

This commit changes the test task that generates new keys to use each of
the different values for the `regenerate` argument, which will ensure
that the module is capable of generating a key when no previous key
exists regardless of the value of `regenerate`. Previously, the task
would always run with the `partial_idempotence` value, and that obscured
a bug (#597) that would occur when it was set to `fail`. The bug was
fixed in the previous commit.

changelogs/fragments/597-openssh_keypair-test-key-creation.yml

@@ -0,0 +1,2 @@
+trivial:
+ - "openssh_keypair - test creating new keys with all values of ``regenerate``"

tests/integration/targets/openssh_keypair/tests/regenerate.yml

@@ -28,6 +28,7 @@
  type: rsa
  size: 1024
  backend: "{{ backend }}"
+ regenerate: "{{ item }}"
  loop: "{{ regenerate_values }}"
 - name: "({{ backend }}) Regenerate - setup password protected keys"
  command: 'ssh-keygen -f {{ remote_tmp_dir }}/regenerate-b-{{ item }} -N {{ passphrase }}'