Impossible to create a new cluster with workers count value equals 0

[olegvn88]

Impossible to create a new cluster with workers count value equals 0

Steps to reproduce:

1. Open the Oshinko Spark Cluster Management home page.
2. Click on "Deploy" button.
3. Input Name of the cluster.
4. Input the "Number of workers" value equals 0.
5. Click on "Deploy" button.

Actual result: The cluster is created with the workers count equals 1.
Expected result: The cluster is created with the workers count equals 0.