Update test.sh to run doctests with single-threaded execution to avoid conflicts

Author: mibes

test.sh

@@ -23,7 +23,7 @@ echo "1/3 running unit tests ..."
 cargo test -- --nocapture
 # most of doctests expect to connect to couchdb running in docker
 echo "2/3 running doctest ..."
-cargo test --doc -- --nocapture
+cargo test --doc -- --nocapture --test-threads=1
 # integration-tests connect to couchdb running in docker
 echo "3/3 running integration tests ..."
 cargo test --features=integration-tests -- --test-threads=1 --nocapture