logcat_parsing: Replace errors when decoding logcat output

Some devices print non standard characters to logcat. If an error
occurs when parsing the output, replace the offending character instead
of raising an error.

wa/workloads/androbench/__init__.py

@@ -43,7 +43,7 @@ class Androbench(ApkUiautoWorkload):
         super(Androbench, self).update_output(context)
         expected_results = len(self.regex_matches)
         logcat_file = context.get_artifact_path('logcat')
-        with open(logcat_file) as fh:
+        with open(logcat_file, errors='replace') as fh:
             for line in fh:
                 for regex in self.regex_matches:
                     match = regex.search(line)