[master] missed /usr in rolling_restart_v2

Author: elliott

Summary: Missed a /usr in front of /bin/env causing rolling_restart_v2 to not work.

Test Plan: execute rolling_restart_v2

Reviewers: aaiyer, rshroff

Reviewed By: rshroff

CC: hbase-eng@

Differential Revision: https://phabricator.fb.com/D1327609

git-svn-id: https://svn.apache.org/repos/asf/hbase/branches/0.89-fb@1595004 13f79535-47bb-0310-9956-ffa450edef68