Back out OOM-Killer adjustment code.

It appears that you must be root to give yourself a negative oom_adj
score and Cassandra generally doesn't run as root.  So this code had
no effect.  A better approach is to modify oom_score_adj in the
init.d scripts that start Cassandra.
Merge pull request #22 from bazaarvoice/ssmith-oomkiller

Back out OOM-Killer adjustment code.