docs: fix typo in kickstart docs: distro_tree -> distro

The osmajor and osversion filters must be applied to distro, not
distro_tree.

Change-Id: Iff07c979f5af005103f005491319ab43575feec3
remove Fedora17-specific kickstart template, merged into Fedora template

The only difference between Fedora and Fedora17 were some one-off
ARM-specific hacks which were not intended to be kept beyond Fedora 17.
But it's easier to keep those in the main Fedora template surrounded by
conditionals, than maintaining two completely separate copies of the
Fedora templates.

Also updated the tests to test for the ARM-specific hacks, and removed
references to Fedora 16 which is now EOL.

Change-Id: I87becc7d974bba26052aa8f899a689a3f154ed96
Merge changes I87becc7d,Iff07c979 into develop

* changes:
  remove Fedora17-specific kickstart template, merged into Fedora template
  docs: fix typo in kickstart docs: distro_tree -> distro