Adds srtts to csv.

calc_bandwidth_goodput_csv.py

         transmission_df["effective_bw_sum"] = transmission_df["nr_effective_bw_sum"] + transmission_df[
             "lte_effective_bw_sum"]
 
-        transmission_df = transmission_df.filter(["goodput", "effective_bw_sum"])
+        transmission_df = transmission_df.filter(["goodput", "effective_bw_sum", "srtt"])
         transmission_df = transmission_df.reset_index(drop=True)
 
         if concat_frame is None:
         else:
             concat_frame = pd.concat([concat_frame, transmission_df])
 
-    concat_frame.to_csv("_concat_bw_gp.csv".format(args.save))
+    concat_frame.to_csv("{}_concat_bw_gp.csv".format(args.save))