tree for embedded server

Test case for bug #56251 "Deadlock with INSERT
DELAYED and MERGE tables" can't be run against
embedded server. Embedded server converts all
DELAYED INSERTs into ordinary INSERTs and this
test can't work properly if such conversion
happens.

Moved this test from merge.test to delayed.test
which is skipped if test suite is run with
--embedded-server option.