Update constants.py so that one can specify environmental variable
ANSIBLE_SYSLOG_FACILITY or syslog_facility in ansible.cfg to define
the syslog facility to use.  Alternatively, you can specify
ansible_syslog_facility in inventory.  Runner now replaces
the syslog facility in the openlog() call with the default or
the injected variables ansible_syslog_facility.

This also updates hacking/test-module to behave similarly.