CORD-706: Bug fix for cases in which ELK logging is turned off.

Change-Id: I164fee218c17dbbb07c45f9af68cf8415bd5307a
diff --git a/xos/xos/logger.py b/xos/xos/logger.py
index 7a358a5..3aff42b 100644
--- a/xos/xos/logger.py
+++ b/xos/xos/logger.py
@@ -125,8 +125,18 @@
         except:
             pass
 
+        self.sanitize_extra_args(cur)
         return cur
 
+    def sanitize_extra_args(self, extra):
+        illegal_keys = logging.LogRecord(None,None,None,None,None,None,None,None).__dict__.keys()
+        for k in illegal_keys:
+            try:
+                del extra[k]
+                self.logger.warn("*** WARNING: Dropped field %s from extra args ***")
+            except KeyError:
+                pass
+
     def info(self, msg, extra={}):
         extra = self.extract_context(extra) 
         self.logger.info(msg, extra=extra)