tests: Close the temp file handle in qa_burst_file_source

This fixes the following warning

./usr/lib64/python3.7/unittest/case.py:645: ResourceWarning: unclosed file <_io.BufferedWriter name='/tmp/tmpkkz_akd6'>
  testMethod()
ResourceWarning: Enable tracemalloc to get the object allocation traceback

Change-Id: I66c2be2e5bf6915e3df253b3a69f5516534e3750
diff --git a/python/qa_burst_file_source.py b/python/qa_burst_file_source.py
index c83c9c4..bfdcc73 100644
--- a/python/qa_burst_file_source.py
+++ b/python/qa_burst_file_source.py
@@ -51,6 +51,7 @@
             0x00, 0x01, 0x01, 0x01, 0x01, 0x00, 0x01, 0x00, 0x01, 0x00, 0x01, 0x00, 0x00, 0x01
             ]))
         handle.flush();
+        handle.close();
 
         src = grgsm.burst_file_source(temp.name);
         dst = grgsm.burst_sink();
@@ -88,6 +89,7 @@
             0x00, 0x01, 0x01, 0x01, 0x01, 0x00, 0x01, 0x00, 0x01, 0x00, 0x01, 0x00, 0x00, 0x01
             ]))
         handle.flush();
+        handle.close();
 
         src = grgsm.burst_file_source(temp.name);
         dst = grgsm.burst_sink();