Judge volume node is error when translate compute node

Judge volume node is error when translate compute node

Currently, when translate a compute node in heat-translator, code is
below:
                 for requires in requirements:
                        for value in requires.values():
                            if isinstance(value, dict):
                                for node_name in value.values():
                                    for n in self.nodetemplates:
                                        if n.name == node_name:
                                            volume_name = node_name
                                            break
                            else:  # unreachable code !
                                for n in self.nodetemplates:
                                    if n.name == node_name:
                                        volume_name = node_name
                                        break
  It's error in nfv tosca because there are more than one
requirements, So the unreachable code will reach.

Notes: the fix will submit to Openstack community.

JIRA:PARSER-92

Change-Id: Ife9c0d28ebe236c04d9d2c02f0025cf774bf6208
Signed-off-by: shangxdy <shang.xiaodong@zte.com.cn>