Change localhost references in test_nested_stack

These references are using localhost which may be running a server and
provide valid responses, contaminating the test. Using RFC2606's
recommended test TLD of '.test' ensures that these will never resolve.

Change-Id: Ie555a321c2af23fbcf4aca9207acb6a0e40bb703
Provide user control for maximum nesting depth

In the case of an infinitely recursing stack, Heat will continue to
keep nesting stacks until python's maximum stack recursion depth
is reached. By this point a lot of memory and time may have been
spent parsing/loading/etc.

The default of 3 is enough to deploy a stack of stacks of stacks. It
can be raised by deployers if there is a desire to do larger and more
complicated stacks, at the cost of more resource utilization.

Fixes bug #1214239

Change-Id: Ic492ef84b94b1f715c49eef7e1794a486fb8182f
Merge "Change localhost references in test_nested_stack"
Merge "Provide user control for maximum nesting depth"