Fix handling of missing logLevel (which means INFO).

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=118694638

Author: b-daniels

src/googleclouddebugger/capture_collector.py

@@ -439,7 +439,7 @@ def __init__(self, definition):
 
     # Select log function.
     level = self._definition.get('logLevel')
-    if level == 'INFO':
+    if not level or level == 'INFO':
       self._log_message = log_info_message
     elif level == 'WARNING':
       self._log_message = log_warning_message