Compress large error attachments

Compress large error attachments

- Verify file size does not exceed release mailing list attachment
  limit and exclude sending the attachment if the file exceeds limits
- Rename file (error.log) and create a compressed file under $WORKSPACE
  so that the file gets archived.
- Update email body with relevent information on the attachment, if
  its not included.

Jira: https://jira.linuxfoundation.org/browse/RELENG-6
Bug: https://bugs.opendaylight.org/show_bug.cgi?id=7977
Change-Id: Id2a6dc168bc0f1b5e6f07ea1ed1d25db7702b5e3
Signed-off-by: Anil Belur <abelur@linuxfoundation.org>