test: reduce concurrency of integration tests

We are seeing odd errors in the integration tests that we can't
repdoduce on workstations. We suspect this may be due to resource
starvation when running in a container in Concourse. By reducing the
number of parallel processes (from 7 to 4) we hope to make the
intermittent failures go away.

[#186912329](https://www.pivotaltracker.com/story/show/186912329)

Makefile

@@ -66,9 +66,10 @@ test: download lint test-units test-integration ## run lint and unit tests
 test-units: deps-go-binary ## run unit tests
 	$(GO) test $(PKG)/brokerapi/... $(PKG)/cmd/... $(PKG)/dbservice/... $(PKG)/internal/... $(PKG)/pkg/... $(PKG)/utils/... -tags=service_broker
 
+# Integration tests are relatively resource-hungry, so we tune down the number of processes that run in parallel
 .PHONY: test-integration
 test-integration: deps-go-binary .pak-cache ## run integration tests
-	PAK_BUILD_CACHE_PATH=$(PAK_CACHE) $(GO) run github.com/onsi/ginkgo/v2/ginkgo -p integrationtest/...
+	PAK_BUILD_CACHE_PATH=$(PAK_CACHE) $(GO) run github.com/onsi/ginkgo/v2/ginkgo --procs 4 integrationtest/...
 
 .pak-cache:
 	mkdir -p $(PAK_CACHE)