haproxy_ctld_daemon.rb: Fix backtrace option

The haproxy_ctld_daemon.rb script in the haproxy cartridge had a typo:
':backgrace' instead of ':backtrace'.

This typo appears to have been present since haproxy_ctld_daemon.rb was
introduced in commit ee8cebbe1adb351a3b80ca3fda4f047aee8fac1b.
Card 57 - provide simple visual branding to the admin console
Card 57 - review feedback
Card 57 - update Gemfiles to use rubygems sass-twitter-bootstrap
Card 57 - make admin console header responsive
Card 57 - make admin console pages responsive
Adding Fedora vs RHEL cases for idler.
Ruby 2.0 in F19 runs as ruby-mri vs ruby in RHEL
<admin-console> broker proxy RPP change + filling in README
<admin-console> adding some configuration options
Card 57 - make histograms responsive
<admin-console> revising packaging
For consistency, rest api response must display 'delete' instead 'destroy' for user/domain/app
Minor tweaks and fixes
Add cartridge and app developers guides
Use service script instead of SIGUSR to reload mcollective
Restructure index; correct missing CSS classes
Merge pull request #3165 from nhr/updates

Add cartridge developer's guide; index refactor
Merge pull request #3152 from jwforres/card_57_admin_console_styling

Merged by openshift-bot
Merge pull request #2981 from Miciah/haproxy_ctld_daemon.rb-fix-typo-backgrace

Merged by openshift-bot
Merge pull request #3156 from kraman/bugfix3

Merged by openshift-bot