rfemu: add max attenuation getter

this allows to query the maximum channel attenuation from within a test case

Change-Id: I35f7cb188790c59bbf2450f78c663fbc9440e406
diff --git a/src/osmo_gsm_tester/obj/rfemu_amarisoftctrl.py b/src/osmo_gsm_tester/obj/rfemu_amarisoftctrl.py
index 6ef25bb..17aa43a 100644
--- a/src/osmo_gsm_tester/obj/rfemu_amarisoftctrl.py
+++ b/src/osmo_gsm_tester/obj/rfemu_amarisoftctrl.py
@@ -59,5 +59,7 @@
         result = self.ws.recv()
         self.dbg('Received CTRL msg: "%s"' % result)
 
+    def get_max_attenuation(self):
+        return 200 # maximum cell_gain value in Amarisoft
 
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