Child process is left behind

[shuse2]

Expected behavior

after shutting down, all child processes should be cleared.
This includes

• Engine
• Plugins

Actual behavior

After shutting down, engine process is still alive

lisk           84117   9.5  0.4 409983184 150224 s002  S     4:01PM   0:01.98 /Users/lisk/.nvm/versions/node/v16.14.1/bin/node /Users/lisk/Documents/10_lisk/lisk-sdk/framework/dist-node/engine_igniter ipc:///Users/lisk/.lisk/pos-mainchain/tmp/sockets/abi.ipc --config /Users/lisk/.lisk/pos-mainch
ain/config/engine_config.json

Steps to reproduce

Start and stop the application with plugin running with child process

Which version(s) does this affect? (Environment, OS, etc...)

6.0.0-alpha.12