Add VPC state.

moto/ec2/models.py

@@ -1280,6 +1280,7 @@ class VPC(TaggedEC2Resource):
         self.id = vpc_id
         self.cidr_block = cidr_block
         self.dhcp_options = None
+        self.state = 'available'
 
     @classmethod
     def create_from_cloudformation_json(cls, resource_name, cloudformation_json):

moto/ec2/responses/vpcs.py

@@ -56,7 +56,7 @@ DESCRIBE_VPCS_RESPONSE = """
     {% for vpc in vpcs %}
       <item>
         <vpcId>{{ vpc.id }}</vpcId>
-        <state>available</state>
+        <state>{{ vpc.state }}</state>
         <cidrBlock>{{ vpc.cidr_block }}</cidrBlock>
         <dhcpOptionsId>dopt-7a8b9c2d</dhcpOptionsId>
         <instanceTenancy>default</instanceTenancy>