added connect exception handling to suppress error message that may reveal
sensitive info - e.g. the entire MongoDB connect string;
turned on MongoCursor::$slaveOkay so ED will use secondary/slaves in a replica set
should the primary/master MongoDB instance go down.

Change-Id: I346b870d40439fa76875ec91ae4a11957b2278a7
Merge "added connect exception handling to suppress error message that may reveal sensitive info - e.g. the entire MongoDB connect string; turned on MongoCursor::$slaveOkay so ED will use secondary/slaves in a replica set should the primary/master MongoDB instance go down."