tests: eldbus: fix heap use after free error detected by address sanitizer

Using the just unref'ed message in the call next line is not going to
end well.

==26321==ERROR: AddressSanitizer: heap-use-after-free on address 0x603000001210 at pc 0x7fc456fd37f5 bp 0x7fff37a00a50 sp 0x7fff37a00a40
READ of size 4 at 0x603000001210 thread T0

    #0 0x7fc456fd37f4 in eldbus_message_path_get ../src/lib/eldbus/eldbus_message.c:193
    #1 0x42f6ab in utc_eldbus_message_ref_unref_p ../src/tests/eldbus/eldbus_test_eldbus_message.c:877
    #2 0x7fc456a27744 in srunner_run_tagged (/lib64/libcheck.so.0+0x6744)
    #3 0x406a01 in _efl_suite_run_end ../src/tests/eldbus/../efl_check.h:282
    #4 0x407357 in _efl_suite_build_and_run ../src/tests/eldbus/../efl_check.h:403
    #5 0x407925 in main ../src/tests/eldbus/eldbus_suite.c:49
    #6 0x7fc45685df32 in __libc_start_main (/lib64/libc.so.6+0x23f32)
    #7 0x405d8d in _start (/home/stefan/EFL/efl/build/src/tests/eldbus/eldbus_suite+0x405d8d)

ref T8142

Reviewed-by: Mike Blumenkrantz <michael.blumenkrantz@gmail.com>
Differential Revision: https://phab.enlightenment.org/D9755

src/tests/eldbus/eldbus_test_eldbus_message.c

@@ -874,7 +874,6 @@ EFL_START_TEST(utc_eldbus_message_ref_unref_p)
    ck_assert_msg(strcmp(path, path_msg) == 0, "%s != %s", path, path_msg);
 
    eldbus_message_unref(msg);
-   ck_assert_ptr_eq(NULL, eldbus_message_path_get(msg));
 
    eldbus_connection_unref(conn);
 }