Bypass throttler for read transactions.
Bypass throttler for read transactions.

Implements a fix for #6072.

JackieXie168/rethinkdb,JackieXie168/rethinkdb,jmptrader/rethinkdb,JackieXie168/rethinkdb,mbroadst/rethinkdb,robertjpayne/rethinkdb,JackieXie168/rethinkdb,jmptrader/rethinkdb,jmptrader/rethinkdb,bpradipt/rethinkdb,robertjpayne/rethinkdb,grandquista/rethinkdb,bpradipt/rethinkdb,jmptrader/rethinkdb,JackieXie168/rethinkdb,mbroadst/rethinkdb,bpradipt/rethinkdb,grandquista/rethinkdb,bpradipt/rethinkdb,bpradipt/rethinkdb,jmptrader/rethinkdb,grandquista/rethinkdb,mbroadst/rethinkdb,robertjpayne/rethinkdb,robertjpayne/rethinkdb,robertjpayne/rethinkdb,grandquista/rethinkdb,grandquista/rethinkdb,jmptrader/rethinkdb,mbroadst/rethinkdb,grandquista/rethinkdb,jmptrader/rethinkdb,bpradipt/rethinkdb,robertjpayne/rethinkdb,JackieXie168/rethinkdb,bpradipt/rethinkdb,jmptrader/rethinkdb,bpradipt/rethinkdb,grandquista/rethinkdb,robertjpayne/rethinkdb,JackieXie168/rethinkdb,JackieXie168/rethinkdb,robertjpayne/rethinkdb,mbroadst/rethinkdb,bpradipt/rethinkdb,mbroadst/rethinkdb,mbroadst/rethinkdb,grandquista/rethinkdb,grandquista/rethinkdb,robertjpayne/rethinkdb,mbroadst/rethinkdb,JackieXie168/rethinkdb,mbroadst/rethinkdb