VOL-3339: Support JSON encoding of log message elements - pyvoltha changes

Change-Id: I3ad7d743b97bc683333a999c0eb28efe29eb053f

  *** Note that there is also a change to the log format in the ONU device adapter (plus a change for this version of PYVOLTHA which I forgot to bump)

Change-Id: I3ad7d743b97bc683333a999c0eb28efe29eb053f
diff --git a/requirements.txt b/requirements.txt
index 9b2d2cb..b49f951 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -18,4 +18,4 @@
 structlog==19.2.0
 transitions==0.6.4
 txaioetcd==0.3.0
-voltha-protos==3.4.1
+voltha-protos==3.4.2