copr-keygen: move handlers to a global place

This used to be a role-specific handler, though we have a special
upgrade playbooks (e.g. copr-keygen-upgrade.yml) that failed because
they use but don't import the copr/* roles (and role handlers).  So we
would have to either import role-specific handlers explicitly, or do
this commit.

handlers/restart_services.yml

@@ -200,3 +200,9 @@
   systemd:
     name: kojira
     state: restarted
+
+- name: restart haveged
+  service: name=haveged state=restarted
+
+- name: restart obs-signd
+  service: name=signd state=restarted

roles/copr/keygen/handlers/main.yml

@@ -1,6 +0,0 @@
----
-- name: restart haveged
-  service: name=haveged state=restarted
-
-- name: restart obs-signd
-  service: name=signd state=restarted