Use F18 disto boto version

Pinning to boto 2.5.2 doesn't work for F18 guests, because it doesn't
work properly with cloud-init 0.7 (ec2 metadata retrieval fails, bug
1158906)

So revert to the Fedora packaged boto, which doesn't work with
heat-cfntools yet (ref bug 1122472), but it does allow intital heat
customization via cloud-init (and cfn-init using local metadata
supplied via nova userdata) to work.
Disable firewalld in F18 templates

Disable firewalld in F18 templates, since leaving it enabled
breaks most of the example templates.  Note that this is in
alignment with the F17 jeos, which has iptables enabled, but it
is not functional due to no /etc/sysconfig/iptables file
Merge pull request #48 from hardys/f18_fixes

Fixes to F18 TDLs