library/ipatest.py: New ipa test module

Test if the krb5.keytab on the machine is valid and can be used.

options:
  servers:
    description: The FQDN of the IPA servers to connect to.
    required: true
  domain:
    description: The primary DNS domain of an existing IPA deployment.
    required: true
  realm:
    description: The Kerberos realm of an existing IPA deployment.
    required: true
  hostname:
    description: The hostname of the machine to join (FQDN).
    required: true
  kdc:
    description: The name or address of the host running the KDC.
    required: true
  principal:
    description: The authorized kerberos principal used to join the IPA realm.
    required: false
  kinit_attempts:
    description: Repeat the request for host Kerberos ticket X times.
    required: false
    default: 5

returns:
  krb5_keytab_ok:
    description: The flag describes if krb5.keytab on the host is usable.
    returned: always
    type: bool