Use of auto that causes a copy

Unnecessary object copies can affect performance. Using the auto keyword leads to an object copy, even if it the variable is unused.
/src/mongo/db/modules/enterprise/src/audit/audit_event.cpp:148: AUTO_CAUSES_COPY 174857 Using the "auto" keyword without an "&" causes the copy of an object of type "std::vector<mongo::HostAndPort, std::allocator<mongo::HostAndPort> >", even if that object is not read.