##### SUMMARY
If you pass aws_kms an existing key_id and no alias, it throws exceptions

##### ISSUE TYPE
- Bug Report

##### COMPONENT NAME
lib/ansible/modules/cloud/amazon/aws_kms.py

##### ANSIBLE VERSION
```
ansible 2.8.2
  config file = /home/mchappel/.ansible.cfg
  configured module search path = [u'/home/mchappel/.ansible/plugins/modules', u'/usr/share/ansible/plugins/modules']
  ansible python module location = /usr/lib/python2.7/site-packages/ansible
  executable location = /usr/bin/ansible
  python version = 2.7.5 (default, Jun 11 2019, 12:19:05) [GCC 4.8.5 20150623 (Red Hat 4.8.5-36)]
```

##### CONFIGURATION
```
DEFAULT_CALLBACK_WHITELIST(/home/mchappel/.ansible.cfg) = [u'timer', u'profile_tasks']
DEFAULT_VAULT_IDENTITY_LIST(/home/mchappel/.ansible.cfg) = [u'original@/home/mchappel/.ansible/secrets/original', u'ssl@/home/mchappel/.ansible/secrets/ssl', u'jenkins@/home/mchappel/.ansible/secrets/jenkins']
HOST_KEY_CHECKING(/home/mchappel/.ansible.cfg) = False
RETRY_FILES_ENABLED(/home/mchappel/.ansible.cfg) = False
```

##### OS / ENVIRONMENT
RHEL7

##### STEPS TO REPRODUCE
```
     - name: Update Policy on key to match AWS Console generate policy
       aws_kms:
        key_id: '{{ new_key["keys"][0]["key_id"] }}'
         policy: "{{ lookup('template', 'console-policy.j2') | to_json }}"
       register: kms_policy_changed
```

##### EXPECTED RESULTS
Key successfully updated


##### ACTUAL RESULTS
Exception.  (There's actually a couple of places that need updating)


##### ADDITIONAL DETAILS
@willthames 

https://github.com/tremble/ansible/tree/aws_kms_keyid_only contains updated tests and a fix.  I'll submit a PR once we know what order everything's likely to get merged in.  Side effect of the change, aws_kms is substantially faster, as a result I had to more the iam_role creation in the test suite.
description: there are invalid (non-ARN) entries in the KMS entry. These don't count as a change, but will be removed if any changes are being made.
  type: bool
  returned: always
'''
statement_label = {
    'role': 'Allow use of the key',
    'role grant': 'Allow attachment of persistent resources',
    'admin': 'Allow access for Key Administrators'
}
from ansible.module_utils.aws.core import AnsibleAWSModule, is_boto3_error_code
from ansible.module_utils.ec2 import ec2_argument_spec
from ansible.module_utils.ec2 import AWSRetry, camel_dict_to_snake_dict
from ansible.module_utils.ec2 import boto3_tag_list_to_ansible_dict, ansible_dict_to_boto3_tag_list
from ansible.module_utils.ec2 import compare_aws_tags, compare_policies
from ansible.module_utils.six import string_types
import json
try:
    import botocore
except ImportError:
    pass  
@AWSRetry.backoff(tries=5, delay=5, backoff=2.0)
def get_iam_roles_with_backoff(connection):
    paginator = connection.get_paginator('list_roles')
    return paginator.paginate().build_full_result()
@AWSRetry.backoff(tries=5, delay=5, backoff=2.0)
def get_kms_keys_with_backoff(connection):
    paginator = connection.get_paginator('list_keys')
    return paginator.paginate().build_full_result()
@AWSRetry.backoff(tries=5, delay=5, backoff=2.0)
def get_kms_aliases_with_backoff(connection):