RFR [15] 8247789: Remove use of reflection from test/jdk/java/io/Serializable/records/StreamRefTest.java

[Chris Hegarty]

This is a small change to remove the use of reflection to fabricate
"bad" serial data - in order to verify constructor invariants for 
record serialization tests. Instead, it is straight forward to just 
modify a single value in the byte stream, that results in the same.

https://cr.openjdk.java.net/~chegar/8247789/webrev/

-Chris.