Fixed bug with dnsmasq startup issue

Hi Steve & Terry,

I have started testing Beta 1e Test6 and discovered that DHCP wasn't starting up when configured through the WebUI (or /etc/config/secn for that matter). I traced the issue to /etc/init.d/config_secn-2. There is testing of the $DHCP_ENABLE setting but there was no "DHCP_ENABLE=`uci get secn.dhcp.enable1`" ahead of that testing so it naturally failed. 

I've added that line into /etc/init.d/config_secn-2 and tested that DHCP now works. 

I'm not sure that I have direct push authority to the stevesong/SECN2-test.git so I forked it first to mrzaphodb/SECN2-test.git, then cloned it to my account on vtbuild, made the modification, commited it, and then pushed it to my forked repo on mrzaphodb. 

This is actually the model we would expect to use with an expanded group of collaborators so this is a good first test of that. Whenever they commit a change to their forked version of the SECN2 repository, they would send one of these pull requests to us and we would examine/test their contribution before merge/committing it to the main repository (currently stevesong/SECN2-test.git). 

Cheers,

Keith