bionic libc test: clean up test for dlopen_null

The test for dlopen function with null specified have been
re-implemented by dlfcn.dladdr test in bionic/tests/dlfcn_test.cpp.
so here deleted it for cleaning up

Change-Id: I99c3d1d2252b41c7484310fa20a1298d80ad565c
Signed-off-by: Yongqin Liu <yongqin.liu@linaro.org>
2 files changed