nfsserver fixes and cleanup

I've been working with the nfsserver and exportfs agents for the past couple of weeks. I'm sure I'll have more fixes/changes, but this current set of changes I have now seems like a good place to start.

Most of what I've done does not affect anyone already using these agents. The only major change here is the removal of the requirement to specify a set of floating ip addresses to the nfsserver agent's nfs_ip option.  This 'nfs_ip' option was used in conjunction with the sm_notify/rpc.statd binaries in an attempt to send SM_NOTIFY requests originating from the floating IPs to the nfs clients.  There are use-cases where this functionality is neither necessary nor desired.  All I did was make nfs_ip argument optional rather than required.

The other changes are minor and mostly only affect the systemd use-case I've been working with for rhel.