Incomplete List when retrieved data from secondary

To reproduce:

git clone https://github.com/fitztrev/rm-issue.git
cd rm-issue


docker compose up -d

docker compose exec sbt sbt "run mongodb://primary:27017,secondary0:27017,secondary1:27017/dbname"

The test will create a dbname.rmbug2 collection, empty it, and insert 2000 documents.

Then it will list the documents from mongodb to stdout with different ReadPreference: secondaryPreferred and primaryPreferred.

Expected: should print 2000 documents. Issue: only print 101 or 202 documents.

Output:

|total document inserted: 2000
|  total result from Secondary Preferred : 0 or 101
|  total result from Primary Preferred   : 2000

To verify the PR fixes the issue:

# in the same `rm-issue` directory
git clone -b fix/1185 https://github.com/tardigradeus/ReactiveMongo.git
cd ReactiveMongo
git tag 1.1.0-RC12-SNAPSHOT


docker compose exec -w /app/ReactiveMongo sbt sbt +publishLocal

Update build.sbt:

-  "org.reactivemongo" %% "reactivemongo" % "1.1.0-RC12",
+  "org.reactivemongo" %% "reactivemongo" % "1.1.0-RC12-SNAPSHOT",

Re-run the test:

docker compose exec sbt sbt "run mongodb://primary:27017,secondary0:27017,secondary1:27017/dbname"

New expected output:

|total document inserted: 2000
|  total result from Secondary Preferred : 2000
|  total result from Primary Preferred   : 2000