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/command.py

@@ -264,6 +264,10 @@ class CommandsSync:
         features = params[0]
         command.cooker.setFeatures(features)
 
+    # although we change the internal state of the cooker, this is transparent since
+    # we always take and leave the cooker in state.initial
+    setFeatures.readonly = True
+
 class CommandsAsync:
     """
     A class of asynchronous commands