qemurunner: Skip conversion from/to binary data for logfile

There is no point in decoding binary data only to encode it again risking
conversion issues. Write the raw data to the log file as binary and skip
the conversion.

Also always update self.msg even if a logfile isn't specified to improve
logging/debug.

(From OE-Core rev: b5d67471dddd198723c4f711747783a33e8e5987)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/lib/oeqa/utils/qemurunner.py

@@ -115,10 +115,9 @@ class QemuRunner:
 
     def log(self, msg):
         if self.logfile:
-            msg = self.decode_qemulog(msg)
-            self.msg += msg
-            with codecs.open(self.logfile, "a", encoding="utf-8") as f:
-                f.write("%s" % msg)
+            with codecs.open(self.logfile, "ab") as f:
+                f.write(msg)
+        self.msg += self.decode_qemulog(msg)
 
     def getOutput(self, o):
         import fcntl