Mtest: make timeouts effective again after bfe9495a72d4
Mtest: make timeouts effective again after bfe9495a72d4

pstack is not even a generic linux tool, so don't rely on its existence

damage here was twofold: mtest tracebacked, and the mserver5 process
stuck didn't get killed at all any more, see tail of
http://monetdb.cwi.nl/testweb/logs/45017:bfe9495a72d4/GNU-Darwin-i386-propcheck/mtest-monetdb5

zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb