Make sure /usr/local/etc/rc.d exists

On 2.2-ALPHA (i386)built on Mon Apr 21 13:01:11 CDT 2014 (for example) there was /usr/local/etc but not /usr/local/etc/rc.d - when I tried to install bandwidthd, that called write_rcfile() which failed because /usr/local/etc/rc.d did not already exist.
Best to check for it and make it if it does not exist.
(I am guessing that the 2.1.n image builds already had /usr/local/etc/rc.d bnefore any packages were installed, otherwise this problem should have already been an issue prior to 2.2)