Fixes #15238 - ignore empty NIC identifiers

(cherry picked from commit 7e20cbac5951b858716268cce29f0fad16b71081)

fixes #15250 - ignore current controller from link_to/hash_for

When link_to generates a link on a page served from a nested controller
(e.g. foreman_example/examples) with a hash of controller/action from
our hash_for_*_path extension, it calls url_for which added the current...

Fixes #15066 - operating systems and ovirt < 3.6

The operating systems endpoint was added in ovirt 3.6
https://bugzilla.redhat.com/show_bug.cgi?id=1050243. Older versions
were failing getting 404 when provisioning.

This patch adds a check for this case. We also cache the operating...

Fixes #6539 - missing templates error is now descriptive

Fixes #15155 - skip single validation when importing puppetclass

Fixes #15182 - limit user taxonomies in API (CVE-2016-4451)

Fixes #14546 - ability to restrict *_external_variables
Fixes #14535 - corrects permissions for smart class parameters

fixes #14905 - enable DHCP orchestration with any boot mode

DHCP orchestration remains useful to set up PXE booting to start the
provisioning process, even when a static boot mode because the boot mode
is typically applied later through templates. It's also useful in image...

Fixes #15174 - make sure to return 404 when taxonomy not found

fixes #13698 - update rest-client and rbovirt gems

- update rest-client to 1.8.x
- update rbovirt to 0.1.x