combo-layer: update() also instance property

The Configuration class mirrors all properties in local hashes.
When updating the configuration, also update these properties
to remain consistent.

(From OE-Core rev: c575ff183ae5c35e0f7e8d90c222994574ce73c9)

Signed-off-by: Patrick Ohly <patrick.ohly@intel.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

scripts/combo-layer

@@ -130,6 +130,7 @@ class Configuration(object):
         parser.set(section, option, value)
         with open(conffile, "w") as f:
             parser.write(f)
+        self.repos[repo][option] = value
 
     def sanity_check(self, initmode=False):
         required_options=["src_uri", "local_repo_dir", "dest_dir", "last_revision"]