Try to stop SOLr shards gracefully before force killing them.

On distributed file systems SOLr may produce lockfiles to control
access to the shard files.  These are not removed if you kill them
with "kill -9".  A normall kill with 1s delay is sufficient to clean
up the lockfiles on CEDA's index node.
Merge pull request #53 from cedadev/stop_solr

Try to stop SOLr shards gracefully before force killing them.
Merge branch 'master' into devel