chimera: Fix duplicate key supression

The postgresql driver for chimera has logic to avoid duplicate key
errors in postgresql while still throwing the SQLException on the
client side.

Unfortunately, the error code used is inconsistent with the error
code used in other logic that supresses the duplicate key error.

This patch resolves the problem: I checked the other places the
modified methods are called, and code that doesn't rely on the
isDuplicateKeyError just checks whther the error code starts with
'23'. This will still work after the change.

Target: trunk
Request: 2.9
Request: 2.8
Request: 2.7
Request: 2.6
Require-notes: yes
Require-book: no
Acked-by: Paul Millar <paul.millar@desy.de>
Patch: http://rb.dcache.org/r/6999/
(cherry picked from commit ee903925e9ea4513b3c553847ad120f62dab5ab3)

Conflicts:
	modules/chimera/src/main/java/org/dcache/chimera/PgSQLFsSqlDriver.java

(cherry picked from commit 5c37c7a19149d36855be1d949b0e91a4585fca2d)
Merge pull request #564 from gbehrmann/fix/2.7/rb6999

Fix/2.7/rb6999