Fixes #9699: Check for nssdb creation before running certutil.

Switches to checking for the nssb execute that creates the actual
database instead of just the directory that contains them. This
prevents the following error on EL6:

  certutil: function failed: SEC_ERROR_LEGACY_DATABASE: The
  certificate/key database is in an unsupported format.

manifests/ssltools/certutil.pp

@@ -1,6 +1,6 @@
 # type to append cert to nssdb
 define certs::ssltools::certutil($nss_db_dir, $client_cert, $cert_name=$title, $refreshonly = true) {
-  File[$nss_db_dir] ->
+  Exec['create-nss-db'] ->
   exec { "delete ${cert_name}":
     path        => ['/bin', '/usr/bin'],
     command     => "certutil -D -d ${nss_db_dir} -n '${cert_name}'",