refactor(sdam): re-use command instead of making Querys

This is the final bit of code that explicitly creates instances of
the `Query` class. We should now be able to completely switch out
OP_QUERY for OP_MSG if it's supported.

NODE-1830

Author: mbroadst

lib/sdam/server.js

@@ -4,7 +4,6 @@ const MongoError = require('../error').MongoError;
 const Pool = require('../connection/pool');
 const relayEvents = require('../utils').relayEvents;
 const calculateDurationInMs = require('../utils').calculateDurationInMs;
-const Query = require('../connection/commands').Query;
 const TwoSixWireProtocolSupport = require('../wireprotocol/2_6_support');
 const ThreeTwoWireProtocolSupport = require('../wireprotocol/3_2_support');
 const BSON = require('../connection/utils').retrieveBSON();
@@ -306,26 +305,17 @@ function extractIsMasterError(err, result) {
 }
 
 function executeServerHandshake(server, callback) {
-  // construct an `ismaster` query
   const compressors =
     server.s.options.compression && server.s.options.compression.compressors
       ? server.s.options.compression.compressors
       : [];
 
-  const queryOptions = { numberToSkip: 0, numberToReturn: -1, checkKeys: false, slaveOk: true };
-  const query = new Query(
-    server.s.bson,
+  server.command(
     'admin.$cmd',
     Object.assign(
       { ismaster: true, client: server.s.clientInfo, compression: compressors },
       saslSupportedMechs(server.s.options)
     ),
-    queryOptions
-  );
-
-  // execute the query
-  server.s.pool.write(
-    query,
     { socketTimeout: server.s.options.connectionTimeout || 2000 },
     callback
   );

lib/topologies/server.js

@@ -8,7 +8,6 @@ var inherits = require('util').inherits,
   debugOptions = require('../connection/utils').debugOptions,
   retrieveBSON = require('../connection/utils').retrieveBSON,
   Pool = require('../connection/pool'),
-  Query = require('../connection/commands').Query,
   MongoError = require('../error').MongoError,
   MongoNetworkError = require('../error').MongoNetworkError,
   TwoSixWireProtocolSupport = require('../wireprotocol/2_6_support'),
@@ -344,24 +343,21 @@ function monitoringProcess(self) {
     // Emit monitoring Process event
     self.emit('monitoring', self);
     // Perform ismaster call
-    // Query options
-    var queryOptions = { numberToSkip: 0, numberToReturn: -1, checkKeys: false, slaveOk: true };
-    // Create a query instance
-    var query = new Query(self.s.bson, 'admin.$cmd', { ismaster: true }, queryOptions);
     // Get start time
     var start = new Date().getTime();
 
     // Execute the ismaster query
-    self.s.pool.write(
-      query,
+    self.command(
+      'admin.$cmd',
+      { ismaster: true },
       {
         socketTimeout:
           typeof self.s.options.connectionTimeout !== 'number'
             ? 2000
             : self.s.options.connectionTimeout,
         monitoring: true
       },
-      function(err, result) {
+      (err, result) => {
         // Set initial lastIsMasterMS
         self.lastIsMasterMS = new Date().getTime() - start;
         if (self.s.pool.isDestroyed()) return;
@@ -389,29 +385,22 @@ var eventHandler = function(self, event) {
     // Handle connect event
     if (event === 'connect') {
       // Issue an ismaster command at connect
-      // Query options
-      var queryOptions = { numberToSkip: 0, numberToReturn: -1, checkKeys: false, slaveOk: true };
       // Create a query instance
       var compressors =
         self.s.compression && self.s.compression.compressors ? self.s.compression.compressors : [];
-      var query = new Query(
-        self.s.bson,
+      // Get start time
+      var start = new Date().getTime();
+      // Execute the ismaster query
+      self.command(
         'admin.$cmd',
         Object.assign(
           { ismaster: true, client: self.clientInfo, compression: compressors },
           getSaslSupportedMechs(self.s.options)
         ),
-        queryOptions
-      );
-      // Get start time
-      var start = new Date().getTime();
-      // Execute the ismaster query
-      self.s.pool.write(
-        query,
         {
           socketTimeout: self.s.options.connectionTimeout || 2000
         },
-        function(err, result) {
+        (err, result) => {
           // Set initial lastIsMasterMS
           self.lastIsMasterMS = new Date().getTime() - start;