[REF] website*: set spinner style in class, instead of inline

This fix is related to:
8298cf6510db906006c43f8c96f712adb2740633
51e399d9acbda42a7ae59226f4302fb7c2a3aed7
9056c58cb8d12d17080ed4e5ede7a6466a0e1f75
Merge branch '8.0' of https://github.com/odoo/odoo into 8.0-linux64