base-files: utilize uci_get_state to read the previous dhcp router address in udhcpc...

base-files: utilize uci_get_state to read the previous dhcp router address in udhcpc default script. The setup_switch() procedure provided by swconfig calls config_load() during network restart and thus confuses udhcpc's uci state keeping resulting in a missing default route on each second network restart. Bypass the cached state vars and query uci directly to make the script immune against unwanted runtime changes.

SVN-Revision: 23211