Non-determinism in the tests was due to results of SBR are different from those gained
with row binlog format.

Because tests effectively verify skipping only ER_DUP_ENTRY it is explicitly required
to run the test on in mixed and stmt binlog format.
ER_DUP_ENTRY is automatically ignored when happened in RBR because of implicit rule
favoring reentrant reading from binlog rule
which means that a Write_rows_log_event overwrites a slave's row
if the one has the same primary key.

If future we might have skipping error due to applying of row-based events.
The comments added saying a new file would be needed for that: rpl_row_skip_error or smth.


mysql-test/suite/rpl/r/rpl_skip_error.result:
  new results
mysql-test/suite/rpl/t/rpl_skip_error-slave.opt:
  wrong error code that can not happen in the test removed.
mysql-test/suite/rpl/t/rpl_skip_error.test:
  enforcing the test is to skip only errors due to SBR.
  The current test does not check anything for RBR as ignorable ER_DUP_ENTRY
  does make sense only for SBR.