SUPEE-3762 Prevent showing install page after refresing SOAP index

Prevents repeated SOAP index page call issue from causing
customers to only see the Magento installation page

Refreshing the SOAP v2 index page (http://your-magento-host-name/index.php/api/v2_soap/index/)
results in all administrators and customers viewing the Magento installation page.
Merge pull request #1 from macopedia/SUPEE-3762

SUPEE-3762 Prevent showing install page after refresing SOAP index