Decrypt ciphertext.

    CLI example::

        salt myminion boto_kms.decrypt encrypted_ciphertext

def decrypt(ciphertext_blob, encryption_context=None, grant_tokens=None,
            region=None, key=None, keyid=None, profile=None):
    '''
    Decrypt ciphertext.

    CLI example::

        salt myminion boto_kms.decrypt encrypted_ciphertext
    '''
    conn = _get_conn(region=region, key=key, keyid=keyid, profile=profile)

    r = {}
    try:
        plaintext = conn.decrypt(
            ciphertext_blob,
            encryption_context=encryption_context,
            grant_tokens=grant_tokens
        )
        r['plaintext'] = plaintext['Plaintext']
    except boto.exception.BotoServerError as e:
        r['error'] = __utils__['boto.get_error'](e)
    return r