Description of problem:
This looks to be an SELinux policy issue.

#============= named_t ==============
allow named_t dnssec_trigger_var_run_t:file write;

type=AVC msg=audit(1419349428.210:456): avc:  denied  { write } for  pid=1777 comm="unbound-control" path="/run/dnssec-trigger/lock" dev="tmpfs" ino=19158 scontext=system_u:system_r:named_t:s0 tcontext=system_u:object_r:dnssec_trigger_var_run_t:s0 tclass=file permissive=0

Version-Release number of selected component:
dnssec-trigger-0.12-15.fc21

Additional info:
reporter:       libreport-2.3.0
cmdline:        /usr/bin/python /usr/libexec/dnssec-trigger-script --update
dso_list:       python-libs-2.7.8-7.fc21.x86_64
executable:     /usr/libexec/dnssec-trigger-script
kernel:         3.17.3-300.fc21.x86_64
runlevel:       N 5
type:           Python
uid:            0

Truncated backtrace:
subprocess.py:540:check_call:CalledProcessError: Command '['unbound-control', 'flush_zone', '.']' returned non-zero exit status 1

Traceback (most recent call last):
  File "/usr/libexec/dnssec-trigger-script", line 480, in <module>
    Application(sys.argv).run()
  File "/usr/libexec/dnssec-trigger-script", line 379, in run
    self.method()
  File "/usr/libexec/dnssec-trigger-script", line 427, in run_update
    self.run_update_global_forwarders()
  File "/usr/libexec/dnssec-trigger-script", line 439, in run_update_global_forwarders
    subprocess.check_call(["unbound-control", "flush_zone", "."])
  File "/usr/lib64/python2.7/subprocess.py", line 540, in check_call
    raise CalledProcessError(retcode, cmd)
CalledProcessError: Command '['unbound-control', 'flush_zone', '.']' returned non-zero exit status 1

Local variables in innermost frame:
cmd: ['unbound-control', 'flush_zone', '.']
retcode: 1
popenargs: (['unbound-control', 'flush_zone', '.'],)
kwargs: {}