SERVER-14123 prevent the explain BSONObj from growing too large

(cherry picked from commit 906cfb13a337fdbdf1b94b773390c4230b059fec)
SERVER-14518: Allow disabling hostname validation for SSL

(cherry picked from commit 138d78bd6d3b28db332f263bd808ccb4f1ac6979)
Merge remote-tracking branch 'upstream/v2.6' into v2.6