Fix lint errors in ldap_user_dn_example parameter

There is no $username variable anywhere in the rabbitmq module.
${username} is not a valid cn. While most likely no one was using
dc=example,dc=com anyway, this patch at least changes the example value
to one that lints.
create /tmp/.rabbitmqadmin.conf
Put rabbitmqadmin.conf in /etc/rabbitmq

This commit puts rabbitmqadmin.conf in /etc/rabbitmq instead of /tmp so
that puppet does not have to replace it if /tmp gets cleared. It also
forces the rabbitmq_exchange provider to call rabbitmqadmin with
-c /etc/rabbitmq/rabbitmqadmin.conf on both destroy and create so that
both operations have access to the contents of the config file.
Merge pull request #283 from cmurphy/ldap

Fix lint errors in ldap_user_dn_example parameter
Merge pull request #281 from cmurphy/alternative_253

Fixes for #253