CA-152387: Add m2crypto dependency to xapi-core

This is needed by the iLO plugin. It used to be pulled in as a
dependency of yum, but that's no longer the case.

Signed-off-by: John Else <john.else@citrix.com>
Merge pull request #2034 from johnelse/ca-152387

CA-152387: Add m2crypto dependency to xapi-core