[eclipselink-dev] Fix checked in for 14330839 - Intermittent ConcurrentM

["Pascal Filion" <pascal.filion@xxxxxxxxxx>]

14330839 - Intermittent ConcurrentModificationException in hrcentral load
testing
https://bug.oraclecorp.com/pls/bug/webbug_edit.edit_info_top?rptno=14330839

Checked into 2.4.1 and main

- The BNF classes that define the JPQL grammar are partially initialized
during creation, a property will be calculate only when required. Even
though the JPQL grammar is a singleton (thread safe), completing the
initialization of the BNF classes was not thread safe.
- The fix involved reworking JPQLQueryBNF to assure thread safety.
- Added unit-tests that attempt to parse JPQL queries in multiple threads
and to make sure there is no potential concurrent modification exception or
dead lock.

Reviewed by John Bracken
Core LRG and JPA FullRegressionTestSuite passed

Pascal...