Set permissions and owner on virtual mail domains

Without the owner being set to vmail and dovecot, when a virtual user
tries to access their mail account, dovecot throws an error that it does
not have permission to create the mail folder for the user.

With the owner and permissions being set the user's mail directory is
created and they can successfully sign in.
Separate virtual mail directory settings into a task

Move the settings of the virtual mail directories into a separate
ansible task.
Merge pull request #91 from ssoriche/master

Set permissions and owner on virtual mail domains