Exponential random backoff for retry
Exponential random backoff for retry

MSP-12460

Recommended by H.D. Moore to prevent two threads trying again at the
same time.  Adapted from explanation of ethernet backoff on wikipedia,
but simplified to use random instead of buckets like ethernet.

rapid7/metasploit-cache,rapid7/metasploit-cache,rapid7/metasploit-cache,rapid7/metasploit-cache