checkcommits: Do not do Fixes check unless requested
checkcommits: Do not do Fixes check unless requested

Running checkcommits without --need-fixes still tries to invoke
the FixesPattern regex (that has not been configured), and results
in NULL deref crash.
Gaurd the FixesPattern regex invocation in a conf.NeedFixes check

Fixes: #147

Signed-off-by: Graham Whaley <95f36e5ac6982f4574a5c449c37cf652e934d2b9@intel.com>

MarioCarrilloA/tests,clearcontainers/tests,devimc/tests,MarioCarrilloA/tests,chavafg/tests,bwarden/tests,chavafg/tests,devimc/tests,GabyCT/tests,GabyCT/tests,bwarden/tests,sboeuf/tests,clearcontainers/tests,sboeuf/tests