Enable Multi-Threads in DeckHand

We are seeing race conditions happening when both drydock and
armada try to retrieve rendered document from deckhand.

This p.s. is meant to prevent 'connection refused' kind of errors
from occuring in such situation.

Change-Id: I9ceca37a1d214fd1a4fe4719db829625289b8d95

entrypoint.sh

@@ -14,12 +14,22 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+set -ex
+
+# Define port
+PORT=${PORT:-9000}
+# Number of uWSGI workers to handle API requests
+DECKHAND_API_WORKERS=${DECKHAND_API_WORKERS:-"1"}
+# Threads per worker
+DECKHAND_API_THREADS=${DECKHAND_API_THREADS:-"4"}
 
 # Start deckhand application
 exec uwsgi \
-    --http :9000 \
+    --http :${PORT} \
     -w deckhand.cmd \
     --callable deckhand_callable \
     --enable-threads \
     -L \
-    --pyargv "--config-file /etc/deckhand/deckhand.conf"
+    --pyargv "--config-file /etc/deckhand/deckhand.conf" \
+    --threads $DECKHAND_API_THREADS \
+    --workers $DECKHAND_API_WORKERS