Do not allow uninterruptible dsme-server to block dsme exit

Try to kill dsme-server first with SIGTERM, then with SIGKILL.

Use maximum child exit wait time that is less than both:
a) watchdog kick period
b) time systemd waits for dmse itself to exit

Do not clear watchdog nowayout states if dsme-server does not exit.

[dsme] Do not allow uninterruptible dsme-server to block dsme exit. Fixes JB#17021
Make forked child process _exit() instead of returning

So that atexit handlers etc inherited from the parent done not
executed prematurely and in the wrong context.
Add missing linefeeds to stderr output
Merge pull request #63 from spiiroin/dsme_server_kill

Do not allow uninterruptible dsme-server to block dsme exit