GetProcessInstanceIdByCorrelation fails with hibernate 4.3

Although jbpm currently uses hibernate 4.2 as JPA provider there are already some users who tried to use jbpm on Wildfly which uses Hibernate 4.3 (JPA 2.1). One of the named queries - GetProcessInstanceIdByCorrelation - does not parse properly sue to use of size function which worked well in 4.2.

Rewrite the query to work on both version to not be dependent on size function to reduce potential issues.