Fix import errors

For Python 2, the lazy importing style uncovered some importing
mistakes. I can't quite figure out how it was working before.

moto/ec2_instance_connect/models.py

@@ -1,4 +1,4 @@
-import boto
+import boto.ec2
 from moto.core import BaseBackend
 
 

moto/rds2/models.py

@@ -8,7 +8,6 @@ from collections import defaultdict
 from boto3 import Session
 from jinja2 import Template
 from re import compile as re_compile
-from moto.cloudformation.exceptions import UnformattedGetAttTemplateException
 from moto.compat import OrderedDict
 from moto.core import BaseBackend, BaseModel
 from moto.core.utils import get_random_hex
@@ -308,6 +307,9 @@ class Database(BaseModel):
                 setattr(self, key, value)
 
     def get_cfn_attribute(self, attribute_name):
+        # Local import to avoid circular dependency with cloudformation.parsing
+        from moto.cloudformation.exceptions import UnformattedGetAttTemplateException
+
         if attribute_name == "Endpoint.Address":
             return self.address
         elif attribute_name == "Endpoint.Port":