Previously-applied patch needs another small fix

Patch applied in commit 4274c596d7429c299467130d8816ea97aebe25bc needed
another small fix.
Minor bug fix of the broctl process command

Added a missing "return" statement to prevent trying to run Bro when
there is a syntax error with the broctl "process" command.

Also removed some redundant lines that were setting a non-zero exit code
twice.