bitbake: bitbake: cooker: mark setFeatures command as read-only

This patch makes sure that the setFeatures command is marked
as read-only and that it can only run if the cooker is in
the initial state.

Additionally, remove logging from the XMLRPC module in favor
of sending the exception to the client for easy processing.

	[YOCTO #6089]

(Bitbake rev: f0a1a3e24757f7658d272035620465f92a3e4c3c)

Signed-off-by: Alexandru DAMIAN <alexandru.damian@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

bitbake/lib/bb/server/xmlrpc.py

@@ -292,7 +292,7 @@ class BitBakeXMLRPCServerConnection(BitBakeBaseServerConnection):
 
         _, error = self.connection.runCommand(["setFeatures", self.featureset])
         if error:
-            logger.error("Unable to set the cooker to the correct featureset: %s" % error)
+            # no need to log it here, the error shall be sent to the client
             raise BaseException(error)
 
         return self