bionic test libc: clean up test for pthread_once

the test implemented in file
    tests/bionic/libc/common/test_pthread_once.c
has been re-implemented in file
    bionic/test/pthread_once_smoke
by the tests pthread.pthread_once_smoke and pthread.pthread_once_1934122,
so here remove the related file and settings

Change-Id: I2c8d6f8a07419d4840512736cf264a86482f7eaf
Signed-off-by: Yongqin Liu <yongqin.liu@linaro.org>
2 files changed