Fix Github Actions failures due to possible rate limiting. (#972)

* Make GitHub actions intergration depend on unit, unit on lint to reduce conccurent load.

This reduces the no. of concurrent actions running at a time, which
should reduce failures due to rate limiting on github.com

* Limit GitHub actions docker build max docker images built at once to be 1

* Increase no. of parallel docker builds to 3 in docker build Github action.

.github/workflows/complete.yml

@@ -6,6 +6,7 @@ jobs:
   build-push-docker-images:
     runs-on: [self-hosted]
     strategy:
+      max-parallel: 3
       matrix:
         component: [core, serving, jobcontroller, jupyter]
     env:
@@ -74,6 +75,7 @@ jobs:
 
   unit-test-java:
     runs-on: ubuntu-latest
+    needs: lint-java
     container: gcr.io/kf-feast/feast-ci:latest
     steps:
       - uses: actions/checkout@v2
@@ -92,6 +94,7 @@ jobs:
 
   unit-test-python:
     runs-on: ubuntu-latest
+    needs: lint-python
     container: gcr.io/kf-feast/feast-ci:latest
     steps:
       - uses: actions/checkout@v2
@@ -102,6 +105,7 @@ jobs:
 
   unit-test-go:
     runs-on: ubuntu-latest
+    needs: lint-go
     container: gcr.io/kf-feast/feast-ci:latest
     steps:
       - uses: actions/checkout@v2
@@ -112,6 +116,7 @@ jobs:
 
   integration-test:
     runs-on: ubuntu-latest
+    needs: unit-test-java
     steps:
       - uses: actions/checkout@v2
       - name: Set up JDK 1.8