ltp: Fix overcommit_memory failure

Backport a patch from upstream to fix the following runtime failure.

mem.c:814: INFO: set overcommit_memory to 0
overcommit_memory.c:213: FAIL: alloc passed, expected to fail

Signed-off-by: He Zhe <zhe.he@windriver.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Armin Kuster <akuster808@gmail.com>