Description of problem:
Exitting fusor-installer at the first (NIC selection) step using ctrl+c causes an traceback to be displayed.
This does NOT happen on the first-ever run of the fusor-installer (for example on first log-in to the freshly installed machine). In that case, after hitting ctrl+c the console disappears.

Version-Release number of selected component (if applicable):
RHCI-6.0-RHEL-7-20151223.t.0-RHCI-x86_64-dvd1.iso

How reproducible:
Always

Steps to Reproduce:
1. Open a console on installed RHCI system
2. Run fusor-installer
3. Hit ctrl+c after it asks you to choose NIC

Actual results:
fusor-installer exits with a traceback in console

Expected results:
fusor-installer should exit quietly, or with a sensible error/warning

Additional info:
Output from fusor-installer:

Select which NIC to use for provisioning:
1. eth0
2. eth1
3. eth2
4. eth3
?  ^C/usr/share/gems/gems/highline-1.6.21/lib/highline.rb:863:in `eof?': Interrupt
	from /usr/share/gems/gems/highline-1.6.21/lib/highline.rb:863:in `get_line'
	from /usr/share/gems/gems/highline-1.6.21/lib/highline.rb:885:in `get_response'
	from /usr/share/gems/gems/highline-1.6.21/lib/highline.rb:260:in `ask'
	from /usr/share/gems/gems/highline-1.6.21/lib/highline.rb:361:in `choose'
	from /usr/share/katello-installer/hooks/lib/provisioning_wizard.rb:284:in `get_interface'
	from /usr/share/katello-installer/hooks/lib/provisioning_wizard.rb:51:in `start'
	from /usr/share/katello-installer/hooks/pre_validations/10-gather_and_set_fusor_values.rb:5:in `block (4 levels) in load'
	from /usr/share/gems/gems/kafo-0.6.5.9/lib/kafo/hooking.rb:32:in `instance_eval'
	from /usr/share/gems/gems/kafo-0.6.5.9/lib/kafo/hooking.rb:32:in `block (4 levels) in load'
	from /usr/share/gems/gems/kafo-0.6.5.9/lib/kafo/hook_context.rb:13:in `instance_exec'
	from /usr/share/gems/gems/kafo-0.6.5.9/lib/kafo/hook_context.rb:13:in `execute'
	from /usr/share/gems/gems/kafo-0.6.5.9/lib/kafo/hooking.rb:49:in `block in execute'
	from /usr/share/gems/gems/kafo-0.6.5.9/lib/kafo/hooking.rb:47:in `each'
	from /usr/share/gems/gems/kafo-0.6.5.9/lib/kafo/hooking.rb:47:in `execute'
	from /usr/share/gems/gems/kafo-0.6.5.9/lib/kafo/kafo_configure.rb:92:in `execute'
	from /usr/share/gems/gems/clamp-0.6.2/lib/clamp/command.rb:67:in `run'
	from /usr/share/gems/gems/clamp-0.6.2/lib/clamp/command.rb:125:in `run'
	from /usr/share/gems/gems/kafo-0.6.5.9/lib/kafo/kafo_configure.rb:116:in `run'
	from /usr/sbin/fusor-installer:63:in `<main>'