Cleanup Rescorer Tests & add random indexing
Add ES_STOP_TIMEOUT/ES_KILL_TIMEOUT variables to packages

This variable allows to configure the waiting time after a TERM signal has
been sent. After that waiting time a KILL signal is sent to ensure the
service is stopped.

In case of a bigger installation the default values might be to slow, so it
now is configurable.

Also, we opted out from sending a KILL signal by default. This has to be
explicitely done by using the ES_KILL_TIMEOUT variable.

Original work done by @tmclaugh at the PR #3719

Closes #3719
Closes #3972