SERVER-9528 retry network failures during document copy at initial sync time
SERVER-6407 When using PLAIN mechanism and $external database, do not digest password by default.

The only use of SASL PLAIN authentication against the $external database is for
LDAP proxy authentication, so this is the intelligent default choice in this scenario.
More readable SocketException::toString()
Reveal latent children before adding a new one
Behave more elegantly when inserting empty field names
SERVER-8943 Remove hard limit of 20,000 incoming connections.
SERVER-9528 need a larger oplog for some builders to avoid RS102
SERVER-9542 Change comparison operator to correct type

Do not use "<" to execute a "<=" comparison.