DHCP failure when rebooting RPI 2

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

i had similar issue i was able to fixed running these commands:

sudo systemctl disable dhcpcd.service
sudo systemctl reboot

the issue seems to be that is that dhcpcd.service is being installed in some update and is not compatible with /etc/network/interfaces