this change migrate the gethostbyname test defined in the old file
system/extras/tests/bionic/libc/common/test_gethostbyname.c
to the new place bionic/tests/netdb_test.cpp
Change-Id: I342171090f681581fb54d68ea4a09adf61f52081 Signed-off-by: Yongqin Liu <yongqin.liu@linaro.org>