Add NFS sec=sys support to ibm.power_aix.filesystem module.

[jrtaisto]

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I need an NFS mount in /etc/filesystems that needs the option sec=sys I can't rely on the AIX filesystem module to create it.

When creating the entry in /etc/filesystems I don't see the code leveraging chnfsmnt using the '-M' anywhere for the NFS mounts to support security_methods.

Also a '-K' support would be nice for the NFS version.

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Want create something like this in an NFS stanza:

    options         = bg,hard,intr,vers=3,sec=sys

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I've considered using the command and shell modules to do this, but figure that's really not the right move long term.

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