tst: Add test for utimes

This patch provides test for utimes. It uses wrapper to read
access and modification times to compare them with ones written by
utimes.

Moreover, access and modification times beyond the Y2038 threshold
date (i.e. 32 bit time_t overflow) are also checked.

Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>