certdb: fix PKCS#12 import with empty password
Since commit f919ab4ee0ec26d77ee6978e75de5daba4073402, a temporary file is
used to give passwords to pk12util. When a password is empty, the temporary
will be empty as well, which pk12util does not like.
Add new line after the password in the temporary file to please pk12util.
https://fedorahosted.org/freeipa/ticket/6541
Reviewed-By: David Kupka <dkupka@redhat.com>