open_posix: fix the sigaction testcase cannot running multi times

[extinguish]

open_posix: fix the ltp_interfaces_sigaction_23_10 deadloop at second run

Signed-off-by: guohao15 [email protected]

[metan-ucw]

I do not get how the test can run multiple times at all, the main() function is called exactly once so there is no need to reset the value at all.