Use SIGTERM handling instead of pulling event file for cancel operation

[de-jcup]

Situation

Currently the PDS cancel operation is handled by scripts and wrapper application via an event file : events/cancel.json

This means a pulling is necessary.

Also the process termination inside PDS process handling uses java process destroy forcibly (means SIGKILL)

Wanted

• The event file shall be still written (for debugging purposes)
• The caller script shall receive a SIGTERM signal
• Only when SIGTERM does not work (after a configurable timeout) a SIGKILL shall be send

Implementation

• Destroy the java helper parts for the event checks (means every usage will be shown as errors in code and can be fixed)
  • if it is used in existing wrapper applications, those applications must implement a
    shutdown handler and do cancel operation there
  • if script helper for events exists, those script parts should also be removed
  • existing caller scripts which check for cancel event shall be changed to treat the
    SIGTERM signal instead (for an example look at the existing PDS SIGTERM delegation
    inside the solutions)
• Directly after writing the event file, the java process (of caller script) must be stopped by
  SIGTERM. For this process.destroy() can be used (see https://hg.openjdk.org/jdk8/jdk8/jdk/file/687fd7c7986d/src/solaris/native/java/lang/UNIXProcess_md.c#l715) for details
• The existing implementation which uses process.destroyForcibly() (means SIGKILL)
  shall be kept as is: This will ensure even when a SIGTERM is ignored/not handled,
  after a while the process will 100% be destroyed when still alive