tcpdump: disable Capsicum if -E option is provided.

The -E is used to provide a secret for decrypting IPsec.
The secret may be provided through command line or as the file.
The problem is that tcpdump doesn't support yet opening files in capability mode
and the file may contain a list of the files to open.

As a workaround, for now, let's just disable capsicum if the -E
the option is provided.

PR:           [[ https://bugs.freebsd.org/236819 | 236819 ]]