Update SystemdService.exists to find all unit files

Author: CarstenGrohmann

testinfra/modules/service.py

@@ -169,14 +169,25 @@ class SystemdService(SysvService):
 
     def _has_systemd_suffix(self):
         """
-        Check if service name has a known systemd unit suffix
+        Check if the service name has a known systemd unit suffix
         """
         unit_suffix = self.name.split(".")[-1]
         return unit_suffix in self.suffix_list
 
     @property
     def exists(self):
-        cmd = self.run_test('systemctl list-unit-files | grep -q "^%s"', self.name)
+        # systemctl offers “list-units” and “list-unit-files” to list unit
+        # files. Unfortunately, neither command provides a complete list of
+        # unit files. Therefore, both commands are queried one after the
+        # other.
+        cmd = self.run_test(
+            r'systemctl list-units --all | grep -q "^[[:space:]]*%s"', self.name
+        )
+        if cmd.rc == 0:
+            return True
+        cmd = self.run_test(
+            r'systemctl list-unit-files | grep -q "^[[:space:]]*%s"', self.name
+        )
         return cmd.rc == 0
 
     @property