Create a new method is_page_ready() method in in the enterprise_policy_base.py to check if a test page 
has completed loading.
Many policy_* autotests have implemented an is_page_ready() method 
to check if the test page has completed loading. 
Replace these individual methods in those tests with a call to a
common method within the enterprise_policy_base.py base class. 


The  is_page_ready() method shall take as an argument, a 'page_ready'
condition/check that signifies that the corresponding test page has completed loading.