testsuite: drop fcntl locking test

Problem: the threadrwlock unit tests is probing documented
fcntl locking behavior, but diod doesn't use it.

Diod locking is currently based on flock rather than fcntl locks,
because fcntl locks are per process not per fd, and diod uses a
thread pool within the same process to service requests.

Having this test isn't relaly helpful.  Drop it.

src/libdiod/Makefile.am

@@ -47,7 +47,6 @@ test_ldadd = \
 
 TESTS = \
 	test_configfile.t \
-	test_threadwrlock.t \
 	test_read.t \
 	test_directory.t \
 	test_lock.t \
@@ -61,9 +60,6 @@ T_LOG_DRIVER = env AM_TAP_AWK='$(AWK)' $(SHELL) \
 test_configfile_t_SOURCES = test/configfile.c
 test_configfile_t_LDADD = $(test_ldadd)
 
-test_threadwrlock_t_SOURCES = test/threadwrlock.c
-test_threadwrlock_t_LDADD = $(test_ldadd)
-
 test_read_t_SOURCES = test/read.c
 test_read_t_LDADD = $(test_ldadd)