Miscellaneous fixes - installation on RedHat and provider defaulting

The cs_commit and cs_shadow types have no default provider. For the other cs_* types the default provider is pcs. This makes pcs the default provider for all types, which silences the "no default provider" warnings.

When cs_shadow resources generate corresponding cs_commit resources, the provider isn't specified and is left to whichever provider Puppet defaults to. This may not be the same as the cs_shadow provider. For example, if cs_shadow is created using the crm provider, the child cs_commit resource will be picked up by pcs, which may result in broken behaviour. This patch passes through the chosen provider to the child resource.

The init.pp contains an exec resource which is invalid, as the resource title is not a valid command and there is no command parameter. The exec resource that is declared on Debian systems in place of this resource enables the daemon by patching /etc/default/corosync, but this is not required on RHEL and is taken care of by the Service['corosync'] resource.

And finally, a couple of typos in the README were fixed :)