NETWORK: In network_diagnostic_report.robot mtr --report output was in bytes

Changes:

  - In network_diagnostic_report.robot  mtr --report command output was in bytes but script expects in string.So changed the format
    by adding "out_buf = out_buf.decode("utf-8")" in lib/utilities.py

Tested:

  - Ran network/network_diagnostic_report.robot script Successfully

Change-Id: I8100035ef24ff654982f4b3b7462b56ae3b72fe5
Signed-off-by: manimozhik <manimozhik@ami.com>
diff --git a/lib/utilities.py b/lib/utilities.py
index 403164b..1ec3b71 100755
--- a/lib/utilities.py
+++ b/lib/utilities.py
@@ -199,6 +199,7 @@
     )
     out_buf, err_buf = sub_proc.communicate()
     shell_rc = sub_proc.returncode
+    out_buf = out_buf.decode("utf-8")
 
     # Split the output by line.
     rows = out_buf.rstrip("\n").split("\n")