DRIVERS-1555: Test that isClientError considers network errors (#1720)

Also use isClientError in estimatedDocumentCount network error tests

Author: jmikola

source/crud/tests/unified/estimatedDocumentCount.json

@@ -130,7 +130,7 @@ tests:
       - name: estimatedDocumentCount
         object: *collection0
         expectError:
-          isError: true
+          isClientError: true
     expectEvents:
       - client: *client0
         events:

source/crud/tests/unified/estimatedDocumentCount.yml

@@ -116,7 +116,7 @@ tests:
         object: *collection1
         name: estimatedDocumentCount
         expectError:
-          isError: true
+          isClientError: true
     expectEvents:
       -
         client: *client1

source/retryable-reads/tests/unified/estimatedDocumentCount.json

@@ -0,0 +1,39 @@
+description: "expectedError-isClientError"
+
+schemaVersion: "1.3"
+
+runOnRequirements:
+  - minServerVersion: "4.0"
+    topologies: [single, replicaset]
+  - minServerVersion: "4.1.7"
+    topologies: [sharded, load-balanced]
+
+createEntities:
+  - client:
+      id: &client0 client0
+      useMultipleMongoses: false
+  - database:
+      id: &database0 database0
+      client: *client0
+      databaseName: &database0Name test
+
+tests:
+  - description: "isClientError considers network errors"
+    operations:
+      - name: failPoint
+        object: testRunner
+        arguments:
+          client: *client0
+          failPoint:
+            configureFailPoint: failCommand
+            mode: { times: 1 }
+            data:
+                failCommands: [ ping ]
+                closeConnection: true
+      - name: runCommand
+        object: *database0
+        arguments:
+          commandName: ping
+          command: { ping: 1 }
+        expectError:
+          isClientError: true