SERVER-11332 ConnectionString less-than for simpler use in maps
(cherry picked from commit 0e3d4410933999e94a5937b08491824138c654d6)
SERVER-11332 minor cleanup of SCC and chunk diff timeout
(cherry picked from commit ac43ecd3c540ad5c191dec27d9fb5a7b0ac4e8f9)
SERVER-11332 multi host query from fastest host using thread pools

(cherry picked from commit f8f57002f72e38d8595674937cd11df42b4ecba7)
(cherry picked from commit db7e5996c7da7d3383ae2c211171bb21ae2b7e00)
SERVER-11332 hookup of fastest query to SyncClusterConnection
(cherry picked from commit d2e4b7d17a8b4a406f053e39f692f394d66e6b11)
Merge remote-tracking branch 'upstream/v2.6' into v2.6