Fixing bug in mongo_validate_ns()
Fixing bug in mongo_validate_ns()

At collection length validation, 'current' point a byte ahead.
This bug make ns validation fail if ns has single character collection.

Elastica/mongo-c-driver-legacy,mongodb/mongo-c-driver-legacy,Elastica/mongo-c-driver-legacy,HeliumProject/mongo-c,HeliumProject/mongo-c,mongodb/mongo-c-driver-legacy,HeliumProject/mongo-c,Elastica/mongo-c-driver-legacy,HeliumProject/mongo-c,Elastica/mongo-c-driver-legacy,mongodb/mongo-c-driver-legacy,mongodb/mongo-c-driver-legacy