[BUG] Minions append to parent process name when multiprocessing=False

[dwoz]

Minions erroneously append Minion._thread_return to the parent process for every job when multiprocessing is set to False.

This results in process names like this:
salt-minion -c etc/salt/ -l info MultiMinionProcessManager MinionProcessManager Minion._thread_return Minion._thread_return Minion._thread_return Minion._thread_return Minion._thread_return Minion._thread_return