handover.py: fix typo in test

Change-Id: I9a52a341d7575807d3e52460e1aa24732e3b3112
diff --git a/sysmocom/suites/4g/handover.py b/sysmocom/suites/4g/handover.py
index 6bb6456..bc49266 100755
--- a/sysmocom/suites/4g/handover.py
+++ b/sysmocom/suites/4g/handover.py
@@ -70,7 +70,7 @@
             print("Exception while terminating process %r" % repr(process))
     raise e
 
-rest_str = 'Got %d successful handovers (>= %d) during %d seconds' % (num_handovers, threshold, duration)
+res_str = 'Got %d successful handovers (>= %d) during %d seconds' % (num_handovers, threshold, duration)
 print(res_str)
 test.set_report_stdout(res_str)
 proc.terminate()