SERVER-15517 use slashes rather than double quotes for escaping in shell launcher

Closes #823

Signed-off-by: Benety Goh <benety@mongodb.com>
SERVER-15597 Fix race condition in dumprestore7.js

Closes #825

Signed-off-by: Benety Goh <benety@mongodb.com>
SERVER-15574 Exception in benchrun when a #VARIABLE is used without a corrosponding let op

Closes #824

Signed-off-by: Benety Goh <benety@mongodb.com>
Merge remote-tracking branch 'upstream/master'