hooks: return 0xD15EA5E for unsafe pthread functions

if a crash was caused by an unsafe pthread function,
the backtrace had the last PC=0xFFFFFx, which isn't helping much.

To make it easier to identify the crash cause,
return 0xD15EA5E ("disease") for those unsafe pthread functions.

Signed-off-by: Adrian Negreanu <adrian.m.negreanu@intel.com>