improve broctl's ability to identify core files

Description

When broctl generates a crash report, it will incorrectly identify a log
file as a core file if the log filename contains the word "core" (note
that none of the default Bro log filenames have this issue).

Environment

None

Assignee

Justin Azoff

Reporter

Daniel Thayer

Labels

None

External issue ID

None

Components

Fix versions

Priority

Normal
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