Log full exec request at VLOG(2)

Change-Id: I0009b6f2642658f6bc32b2fb1a65f9d445dca596
Reviewed-on: http://gerrit.ent.cloudera.com:8080/3308
Reviewed-by: Nong Li <nong@cloudera.com>
Tested-by: jenkins
(cherry picked from commit 112c451c5466b38a048182cd37f9b0eb9589ab4b)
Reviewed-on: http://gerrit.ent.cloudera.com:8080/3466
Reviewed-by: Henry Robinson <henry@cloudera.com>