nitb_netreg_mass: Allow a suite to configure num subscriber

Remove hardcoded configuration and replace it with a reservation in
the suite.

Change-Id: Ic9fd560c2924731e4fd6eea5aaf3ad565cb4ef52
diff --git a/src/osmo_gsm_tester/suite.py b/src/osmo_gsm_tester/suite.py
index db580ec..aefdc24 100644
--- a/src/osmo_gsm_tester/suite.py
+++ b/src/osmo_gsm_tester/suite.py
@@ -344,6 +344,15 @@
             l.append(self.modem())
         return l
 
+    def all_resources(self, resource_func):
+        """Returns all yielded resource."""
+        l = []
+        while True:
+            try:
+                l.append(resource_func())
+            except resource.NoResourceExn:
+                return l
+
     def esme(self):
         esme_obj = esme.Esme(self.msisdn())
         self.register_for_cleanup(esme_obj)