Add notes on yum.conf and syslog
Add notes on yum.conf and syslog

Fixing the logging issues in 3b8b6de uncovered some interesting info
about how yum handles syslog. This commit adds that to the top docstring
for the yumpkg module, as it may prove useful to users.

saltstack/salt,saltstack/salt,saltstack/salt,saltstack/salt,saltstack/salt