[Murano] Murano can't deploy environment with default network parameter (Create New)

[Victor Ryzhenkin]

Bug was found in custom iso with Murano.

Steps:
1. Upload app
2. Create environment without existing network (Leave the field with network dafault)
3. Add app
4. Deploy environment

Actual result:
Deploy failed with error
"exceptions.StopIteration:"

Trace in murano-engine:
2015-07-22 18:43:08.534 24727 ERROR murano.common.engine [-]
  exceptions.StopIteration:
  Traceback (most recent call last):
    File "/tmp/murano-packages-cache/34c0b923-d225-4752-a1f5-31f8849b31ce/io.murano/Classes/Environment.yaml", line 74:9 in method deploy of class io.murano.Environment
        $.applications.pselect($.deploy())
    File "/tmp/murano-packages-cache/34c0b923-d225-4752-a1f5-31f8849b31ce/io.murano.apps.Simple/Classes/Simple.yaml", line 28:13 in method deploy of class io.murano.apps.Simple
        $.instance.deploy()
    File "/tmp/murano-packages-cache/34c0b923-d225-4752-a1f5-31f8849b31ce/io.murano/Classes/resources/Instance.yaml", line 90:9 in method deploy of class io.murano.resources.Instance
        $.ensureNetworksDeployed()
    File "/tmp/murano-packages-cache/34c0b923-d225-4752-a1f5-31f8849b31ce/io.murano/Classes/resources/Instance.yaml", line 154:13 in method ensureNetworksDeployed of class io.murano.resources.Instance
        $.environment.defaultNetworks.environment.deploy()
    File "/tmp/murano-packages-cache/34c0b923-d225-4752-a1f5-31f8849b31ce/io.murano/Classes/resources/ExistingNeutronNetwork.yaml", line 45:33 in method deploy of class io.murano.resources.ExistingNeutronNetwork
        $._getNetworks().where( $.name = $this.internalNetworkName or $.id = $this.internalNetworkName).first().id
    File "/usr/lib/python2.7/dist-packages/murano/dsl/helpers.py", line 66 in method evaluate
        return execute_instruction(value, func, context)
    File "/usr/lib/python2.7/dist-packages/murano/dsl/helpers.py", line 52 in method execute_instruction
        result = action()
    File "/usr/lib/python2.7/dist-packages/murano/dsl/helpers.py", line 62 in method <lambda>
        func = lambda: evaluate(value.evaluate(context), context, 1)
    File "/usr/lib/python2.7/dist-packages/murano/dsl/yaql_expression.py", line 75 in method evaluate
        return self._parsed_expression.evaluate(context=context)
    File "/usr/lib/python2.7/dist-packages/yaql/expressions.py", line 35 in method evaluate
        return f()
    File "/usr/lib/python2.7/dist-packages/yaql/expressions.py", line 73 in method __call__
        this = self.obj_wrapper()
    File "/usr/lib/python2.7/dist-packages/yaql/expressions.py", line 100 in method __call__
        return self._try_invoke(fs, args_to_pass, context)
    File "/usr/lib/python2.7/dist-packages/yaql/expressions.py", line 112 in method _try_invoke
        return func(*args_to_pass)
    File "/usr/lib/python2.7/dist-packages/murano/engine/system/yaql_functions.py", line 327 in method _first
        return iter(collection).next()

There is one more concern about this bug.
The exception non-informative for user.
Also, this bug will blocks swarm job and all deployment tests.