Add back AUTOTEST to 'check' targets; remove '+'
- AUTOTEST is a convenience make variable. e.g.: make AUTOTEST=--stress check
- '+' says to ignore '-n' and '-t' make flags.


git-svn-id: svn://svn.code.sf.net/p/dmtcp/code/trunk@2409 ba6dc0ae-232f-0410-883f-9ebac64fc565