PYTHON-3024 Update estimatedDocumentCount test for Atlas Data Lake (#802)

Migrate data lake testing to ubuntu 18.
Ensure mongohouse downloads the right build via VARIANT.

Author: ShaneHarvey

.evergreen/config.yml

@@ -310,7 +310,9 @@ functions:
         script: |
           set -o xtrace
           ${PREPARE_SHELL}
-          bash ${DRIVERS_TOOLS}/.evergreen/atlas_data_lake/build-mongohouse-local.sh
+          # The mongohouse build script needs to be passed the VARIANT variable, see
+          # https://github.com/10gen/mongohouse/blob/973cc11/evergreen.yaml#L65
+          VARIANT=ubuntu1804 bash ${DRIVERS_TOOLS}/.evergreen/atlas_data_lake/build-mongohouse-local.sh
     - command: shell.exec
       type: setup
       params:
@@ -2439,7 +2441,7 @@ buildvariants:
 
 - matrix_name: "data-lake-spec-tests"
   matrix_spec:
-    platform: ubuntu-16.04
+    platform: ubuntu-18.04
     python-version: ["3.6", "3.9"]
     auth: "auth"
     c-extensions: "*"

test/data_lake/estimatedDocumentCount.json

@@ -15,8 +15,25 @@
         {
           "command_started_event": {
             "command": {
-              "count": "driverdata"
-            }
+              "aggregate": "driverdata",
+              "pipeline": [
+                {
+                  "$collStats": {
+                    "count": {}
+                  }
+                },
+                {
+                  "$group": {
+                    "_id": 1,
+                    "n": {
+                      "$sum": "$count"
+                    }
+                  }
+                }
+              ]
+            },
+            "command_name": "aggregate",
+            "database_name": "test"
           }
         }
       ]

test/data_lake/getMore.json

@@ -54,4 +54,4 @@
       ]
     }
   ]
-}
+}

test/data_lake/listCollections.json

@@ -22,4 +22,4 @@
       ]
     }
   ]
-}
+}

test/data_lake/listDatabases.json

@@ -21,4 +21,4 @@
       ]
     }
   ]
-}
+}

test/data_lake/runCommand.json

@@ -28,4 +28,4 @@
       ]
     }
   ]
-}
+}