main/cli: Do not attempt to show CDR data for internal channels

Internal channels don't have CDRs. Querying the CDR engine for their variables
will make it cranky.
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Merged revisions 422506 from http://svn.asterisk.org/svn/asterisk/branches/12
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Merged revisions 422507 from http://svn.asterisk.org/svn/asterisk/branches/13


git-svn-id: http://svn.asterisk.org/svn/asterisk/trunk@422524 f38db490-d61c-443f-a65b-d21fe96a405b