Protocol v4 added WRITE_FAILURE and READ_FAILURE. When running under v3
we downgrade these exceptions to WRITE_TIMEOUT and READ_TIMEOUT (since
the client won't understand the v4 errors), but we still send the new
error codes. This causes the client to become confused.
Fix by updating the error codes.
A better fix is to move the error code from the constructor parameter
list and hard-code it in the constructor, but that is left for a follow-up
after this minimal fix.
Fixes#5610.
Closes#10362
987e6533d2