Add nim alt_disk_install feature

[opokam]

When patching nim client LPARs with SP or TL patch sets it is best to patch to an alternative copy of the rootvg. Unless the documentation is behind, we do not see the nim -o alt_disk_install option. Please add this feature as we have just started exploring ansible AIX.

[nitismis]

Thanks for the request, we will include this in our list of enhancements.