Yet another setenv(LD_PRELOAD, ...) fix.

git-svn-id: svn://svn.code.sf.net/p/dmtcp/code/trunk@2750 ba6dc0ae-232f-0410-883f-9ebac64fc565
Minor cleanup.

git-svn-id: svn://svn.code.sf.net/p/dmtcp/code/trunk@2751 ba6dc0ae-232f-0410-883f-9ebac64fc565