schedule: strip out targets
schedule: strip out targets

If the user feeds in a yaml with targets, the worker will launch the job
but fail with

2013-09-03T11:18:34.333 CRITICAL:root:AssertionError: You cannot specify targets in a config file when using the --lock option

Just strip them out before scheduling.  This eases my personal workflow
where I have a test I'm running manually against some prelocked machines
but also want to schedule it.

Signed-off-by: Sage Weil <6dd34506bbd5e58221bbb3e4732d97c91f02277b@inktank.com>

zhouyuan/teuthology,dmick/teuthology,robbat2/teuthology,dmick/teuthology,zhouyuan/teuthology,tchaikov/teuthology,yghannam/teuthology,yghannam/teuthology,t-miyamae/teuthology,robbat2/teuthology,tchaikov/teuthology,ceph/teuthology,ivotron/teuthology,michaelsevilla/teuthology,SUSE/teuthology,caibo2014/teuthology,SUSE/teuthology,ivotron/teuthology,ktdreyer/teuthology,caibo2014/teuthology,dreamhost/teuthology,michaelsevilla/teuthology,dreamhost/teuthology,ceph/teuthology,SUSE/teuthology,dmick/teuthology,ktdreyer/teuthology,t-miyamae/teuthology