Uplift celery to address memory leak

Uplifted celery to 4.4.2 to address memory leak issue raised
in:  https://github.com/celery/celery/issues/4843.
This issue is addressed in celery 4.4.2

Change-Id: I26c403513ba48308044d69130d33561b314fd209

src/bin/shipyard_airflow/requirements.txt

@@ -16,6 +16,7 @@
 
 alembic==1.0.0
 arrow==0.12.1
+celery~=4.4.2
 configparser==3.5.0
 cryptography==2.3
 falcon==1.4.1

src/bin/shipyard_client/test-requirements.txt

@@ -1,5 +1,5 @@
 # Testing
-amqp==2.5.1
+amqp~=2.6.0
 pytest==3.5.0
 pytest-cov==2.5.1
 responses==0.10.2