ipatests: fixture can produce IndexError

The fixture issue_and_expire_acme_cert returns a function
that fills the hosts array. If the function is not called in
the test (for instance because a test is skipped, as in
TestACMEPrune::test_prune_cert_search_size_limit), hosts = []
and hosts[0] raises an IndexError.

Fix the fixture to check first that hosts is not empty.

Related: https://pagure.io/freeipa/issue/9348

Signed-off-by: Florence Blanc-Renaud <flo@redhat.com>
Reviewed-By: Mohammad Rizwan Yusuf <myusuf@redhat.com>

ipatests/test_integration/test_acme.py

@@ -633,9 +633,13 @@ def _issue_and_expire_acme_cert(
         tasks.move_date(host, 'start', '-90days-60minutes')
 
     # restart ipa services as date moved and wait to get things settle
-    time.sleep(10)
-    hosts[0].run_command(['ipactl', 'restart'])
-    time.sleep(10)
+    # if the internal fixture was not called (for instance because the test
+    # was skipped), hosts = [] and hosts[0] would produce an IndexError
+    # exception.
+    if hosts:
+        time.sleep(10)
+        hosts[0].run_command(['ipactl', 'restart'])
+        time.sleep(10)
 
 
 class TestACMERenew(IntegrationTest):