Re-initialize NSS database after otptoken plugin tests
OTP token tests do not properly reinitialize the NSS db, thus
making subsequent xmlrpc tests fail on SSL cert validation.
Make sure NSS db is re-initalized in the teardown method.
https://fedorahosted.org/freeipa/ticket/4748
Reviewed-By: Petr Vobornik <pvoborni@redhat.com>
Reviewed-By: Petr Viktorin <pviktori@redhat.com>