Enable logging to syslog via logging module.

Besides the program's stdout/stderr, it will also print the user who
triggered the execution as well as the whole command that was
triggered.

   May 13 19:48:27 laptop nixops[18049]: User: rbvermaa, Command: /nix/store/bjwf978h1f56hkb7c0x40msmp8865879-nixops-0/bin/.nixops-wrapped check -d wordpress