##### 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.
Action:
      - "kms:Encrypt"
      - "kms:Decrypt"
      - "kms:ReEncrypt*"
      - "kms:GenerateDataKey*"
      - "kms:CreateGrant"
      - "kms:DescribeKey"
      Resource: "*"
      Condition:
        StringEquals:
          kms:CallerAccount: "111111111111"
          kms:ViaService: "ec2.ap-southeast-2.amazonaws.com"
    - Sid: "Allow direct access to key metadata to the account"
      Effect: "Allow"
      Principal:
        AWS: "arn:aws:iam::111111111111:root"
      Action:
      - "kms:Describe*"
      - "kms:Get*"
      - "kms:List*"
      - "kms:RevokeGrant"
      Resource: "*"
tags:
  description: dictionary of tags applied to the key
  type: dict
  returned: always
  sample:
    Name: myKey
    Purpose: protecting_stuff
grants: