Configuration read when system bootup

Current when system bootup, it reads the default parameters defined in the yang files. When system is running, if we change the parameters in the configuration file (org.opendaylight.openflowplugin.cfg), the karaf/blueprint will invoke the update() methods of the OpenFlowPluginProviderImpl.class to update the parameters dynamically. However, the system will not read the parameters in the configuration file when it bootup, which leads to confusion. For example, if we set the parameters in the configuraiion file before system bootup and keep them unchanged in the system running, the system will never read this parameters.

to make things correct, when system bootup, first it need to read default parameters defined in the yang files, and then read the parameters defined in the configuration file.