##### 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.
if filtr[0] == 'key-id':
        return filtr[1] == key['key_id']
    if filtr[0] == 'tag-key':
        return filtr[1] in key['tags']
    if filtr[0] == 'tag-value':
        return filtr[1] in key['tags'].values()
    if filtr[0] == 'alias':
        return filtr[1] in key['aliases']
    if filtr[0].startswith('tag:'):
        return key['Tags'][filtr[0][4:]] == filtr[1]
def key_matches_filters(key, filters):
    if not filters:
        return True
    else:
        return all([key_matches_filter(key, filtr) for filtr in filters.items()])
def camel_to_snake_grant(grant):
    ''' camel_to_snake_grant snakifies everything except the encryption context '''
    constraints = grant.get('Constraints', {})
    result = camel_dict_to_snake_dict(grant)
    if 'EncryptionContextEquals' in constraints:
        result['constraints']['encryption_context_equals'] = constraints['EncryptionContextEquals']
    if 'EncryptionContextSubset' in constraints:
        result['constraints']['encryption_context_subset'] = constraints['EncryptionContextSubset']
    return result
def get_key_details(connection, module, key_id):