ISPN-3289 PutForExternalRead should only write the value on the originator once

https://issues.jboss.org/browse/ISPN-3289

Use the same condition to decide whether a PFER should write to the data
container as for a non-tx put, even in tx caches.

Should fix random failures in PutForExternalReadDistOptimisticTest.testNoOpWhenKeyPresent