Incorrect return code for error on call of commit during 2PC

Hi,

it seems that PostgreSQL jdbc driver returns incorrect code on call of 'commit' during 2PC. Currently the driver
returnsXAER_RMERR. 
I expect that it's this call
https://github.com/pgjdbc/pgjdbc/blob/master/org/postgresql/xa/PGXAConnection.java#L528

But the XA spec (http://pubs.opengroup.org/onlinepubs/009680699/toc.pdf) says for XAER_RMERR that
"An error occurred in committing the work performed on behalf of the transaction
branch and the branch’s work has been rolled back. Note that returning this error
signals a catastrophic event to a transaction manager since other resource
managers may successfully commit their work on behalf of this branch. This error
should be returned only when a resource manager concludes that it can never
commit the branch and that it cannot hold the branch’s resources in a prepared
state. Otherwise, [XA_RETRY] should be returned."

In case there is longer discussion about scenario hitting this issue and about handling this at RedHat bugzilla here:
https://bugzilla.redhat.com/show_bug.cgi?id=988724

From what is said here I think that PostgreSQL database should rollback the transaction itself and then it could return
XAExceptionerror code XAER_RMERR or it should return 
XAER_RMFAIL or XAER_RETRY.

Would you mind my opening a issue for PostgreSQL jdbc driver?

Thank you
Ondra Chaloupka