The fact that you get an IP address obtained via DHCP means that there is another DHCP client active on your Raspberry. You can check how many clients are installed by running the following command:
dpkg -l | grep dhcp
In my case (Raspberry Pi 2 image from 5th May) I got:
ii dhcpcd5 6.7.1-1+rpi1 armhf DHCPv4, IPv6RA and DHCPv6 client with IPv4LL support ii isc-dhcp-client 4.2.2.dfsg.1-5+deb70u6 armhf ISC DHCP client ii isc-dhcp-common 4.2.2.dfsg.1-5+deb70u6 armhf common files used by all the isc-dhcp* packages
So obviously there are two DHCP clients installed (dhcpcd5 and isc-dhcp-client). DHCPCD detects the existence of the another client and does not start, showing the error. To get rid of the error you can remove the dhcpcd client:
apt-get remove dhcpcd5