Description of problem:
When provision the template URL is taken from the Subnets TFTP Capsule, we should instead have a Template Capsule option.

In situations where you don't want to run a TFTP server and are using Bootdisk ISO's for provisioning you will be unable to provision via a Capsule as the KS path in the PXELinux template will look for the Subnets TFTP Capsule and use that for provision, if that fails it defaults back to the Satellite URL (this is why its only a problem when using Capsules).

As a workaround you have to enable TFTP featue on the Capsule.

How reproducible:
Always

Steps to Reproduce:
1. See below

Additional info:

<sean> jsherrill one other thing, the PXELinux template is pointing to the satellite :(
<jsherrill> sean: for the kickstart file you mean?
<jsherrill> sean: i think the host has to be associated with a subnet, that has a template proxy set
<sean> "Kickstart default PXELinux" template had ...ks=http://<sat url>/blah it should be ks=http://<capsule url>/blah
<sean> which option is it on the subnet? 
<sean> jsherrill, capsule tab only has DHCP TFTP DNS Discovery & Remote-ex ?
<jsherrill> sean: if you go to your capsule list, do you have a capsule with the 'template' feature ?
<jsherrill> its either called 'template' or 'template proxy'
<jsherrill> sean:  you may need to provide another install option
<sean> jsherrill, yup they all have templates enabled
<sean> jsherrill, updated the foreman_url setting to point to capsule for now 
<sean> jsherrill looks like its looking for tftp capsule https://github.com/theforeman/foreman/blob/develop/app/models/concerns/host_template_helpers.rb#L34
<sean> jsherrill, i think we should create a new template capsule option?
<sean> becuase you might want to a capsule for templates and not tftp, e.g using bootdisk 
<jsherrill> ohhh right it piggy backs off that
<jsherrill> sean: in that case it wouldn't really matter if the tftp was updated right? 
<jsherrill> or do you not have a tftp feature on that proxy
<jsherrill> you could enable that feature on the proxy and it shouldn't hurt anything if you're not using the tftp server there
<sean> i dont have tftp enabled, looks like im going to have to enable it and set the capsule as a 'better' fix for now
<jsherrill> sean: yeah, i think thats the best best for the shorter term
<jsherrill> but i agree, having that as an option on the subnet
<jsherrill> would be good
<jsherrill> so you don't have to have a dummy tftp server