##### 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.
ret = kms.list_aliases()
    key_id = None
    for a in ret['Aliases']:
        if a['AliasName'] == aliasname:
            key_id = a['TargetKeyId']
            break
    if not key_id:
        raise Exception('could not find alias {0}'.format(aliasname))
    
    
    ret = kms.list_keys()
    for k in ret['Keys']:
        if k['KeyId'] == key_id:
            return k['KeyArn']
    raise Exception('could not find key from id: {0}'.format(key_id))
def get_arn_from_role_name(iam, rolename):
    ret = iam.get_role(RoleName=rolename)
    if ret.get('Role') and ret['Role'].get('Arn'):
        return ret['Role']['Arn']
    raise Exception('could not find arn for name {0}.'.format(rolename))
def do_policy_grant(kms, keyarn, role_arn, granttypes, mode='grant', dry_run=True, clean_invalid_entries=True):