Override new default for --maxNonVolatileBuffers on backups
Override new default for --maxNonVolatileBuffers on backups

The value was reduced recently to control memory usage, but it
slowed down recovery. The override restores recovery performance
back to what it used to be.
recovery times drop back to where they used to be.
recovery times drop back to where they used to be.

SMatsushi/RAMCloud,matrix207/RAMCloud,alexandermerritt/ramcloud,jblomer/ramcloud,alexandermerritt/ramcloud,alexandermerritt/ramcloud,alexandermerritt/ramcloud,utah-scs/RAMCloud,SMatsushi/RAMCloud,anirajk/RAMCloud,jblomer/ramcloud,matrix207/RAMCloud,utah-scs/RAMCloud,anirajk/RAMCloud,anirajk/RAMCloud,utah-scs/RAMCloud,utah-scs/RAMCloud,rstutsman/RAMCloud,jblomer/ramcloud,rstutsman/RAMCloud,SMatsushi/RAMCloud,jblomer/ramcloud,anirajk/RAMCloud,matrix207/RAMCloud,rstutsman/RAMCloud,matrix207/RAMCloud,rstutsman/RAMCloud,anirajk/RAMCloud,alexandermerritt/ramcloud,SMatsushi/RAMCloud,anirajk/RAMCloud,rstutsman/RAMCloud,SMatsushi/RAMCloud,SMatsushi/RAMCloud,jblomer/ramcloud,jblomer/ramcloud,matrix207/RAMCloud,utah-scs/RAMCloud,utah-scs/RAMCloud,alexandermerritt/ramcloud,rstutsman/RAMCloud,matrix207/RAMCloud