pcs_cluster: allow choosing the ip_version on cluster creation

[OndrejHome]

Idea:

• implement ip_version attribute to give ability to set IP version based on which version of transport+pcs_version is being used
• possible combinations should be targetting CentOS 7 and Fedora29 as seen in corosync man page below

Expectations:

• edit pcs_cluster module in way that implements above
• don't forget to provide documentation about the attribute in module itself

In case you would like to work on this, please just drop a comment here so I'm aware of it.

---

pcs-0.9/corosync-2.4

ip_version
     Specifies version of IP to use for communication. Value can be one of ipv4 or ipv6. Default (if unspecified) is ipv4.

pcs-0.10/corosync-3.0

ip_version
      This specifies version of IP to ask DNS resolver for.  The value can be one of ipv4 (look only for an IPv4 address) , ipv6 (check  only  IPv6
      address) , ipv4-6 (first check IPv4 address, if that fails then look for an IPv6 address) and ipv6-4 (first check IPv6 address, if that fails
      then look for an IPv4 address).

      Default (if unspecified) is ipv6-4 for knet and udpu transports and ipv4 for udp.

      Knet transport allows to have a both ipv4 and ipv6 address, provided they are consistent on each link.