Fix json formatting mistakes

scripts/txtime_stats.py

@@ -36,8 +36,9 @@ def compute_offsets_stats(file_path, interval):
     measure_set["measure_type"] = "packet_jitter_tcpdump"
     measure_set["props_names"] = ["packet_jitter_tcpdump"]
     measure_set["units"] = ["us"]
-    measure_set["props_type"] = ["histogram"]
+    measure_set["props_type"] = "histogram"
     measure_set["metadata"] = {"i": interval}
+    measure_set["middle"] = 1000
 
     histogram = [0 for i in range(0, 2000)]
 
@@ -73,7 +74,7 @@ def compute_offsets_stats(file_path, interval):
     measure_set["props"] = [histogram]
 
     data = {}
-    data["measure_sets"] = [{"measure_sets": measure_set}]
+    data["measure_sets"] = [measure_set]
 
     path = "tcpdump_histogram"