##### 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.
try:
        result = get_kms_metadata_with_backoff(connection, key_id)['KeyMetadata']
    except (botocore.exceptions.ClientError, botocore.exceptions.BotoCoreError) as e:
        module.fail_json_aws(e, msg="Failed to obtain key metadata")
    result['KeyArn'] = result.pop('Arn')
    try:
        aliases = get_kms_aliases_lookup(connection)
    except (botocore.exceptions.ClientError, botocore.exceptions.BotoCoreError) as e:
        module.fail_json_aws(e, msg="Failed to obtain aliases")
    result['aliases'] = aliases.get(result['KeyId'], [])
    result = camel_dict_to_snake_dict(result)
    
    try:
        result['grants'] = [camel_to_snake_grant(grant) for grant in
                            get_kms_grants_with_backoff(connection, key_id)['Grants']]
    except (botocore.exceptions.ClientError, botocore.exceptions.BotoCoreError) as e:
        module.fail_json_aws(e, msg="Failed to obtain key grants")
    tags = get_kms_tags(connection, module, key_id)
    result['tags'] = boto3_tag_list_to_ansible_dict(tags, 'TagKey', 'TagValue')
    result['policies'] = get_kms_policies(connection, module, key_id)
    return result
def get_kms_facts(connection, module):
    try:
        keys = get_kms_keys_with_backoff(connection)['Keys']
    except (botocore.exceptions.ClientError, botocore.exceptions.BotoCoreError) as e:
        module.fail_json_aws(e, msg="Failed to obtain keys")
    return [get_key_details(connection, module, key['KeyId']) for key in keys]
def convert_grant_params(grant, key):