LU-6081 user: adding llapi_create_volatile_param()

LU-6081 user: adding llapi_create_volatile_param()

This new function is similar to the existing
llapi_create_volatile_idx() function, but takes 2 additional
parameters: a stripe information, and a file mode.

llapi_create_volatile_idx() is changed to use
llapi_create_volatile_param().

Include a new man page for llapi_create_volatile_param(),
llapi_create_volatile_idx() and llapi_create_volatile_param().

Signed-off-by: frank zago <fzago@cray.com>
Change-Id: Ia50750d68b8cfa335b53b114a20fccaed49c75cd
Reviewed-on: https://review.whamcloud.com/13242
Tested-by: Jenkins
Reviewed-by: John L. Hammond <jhammond@whamcloud.com>
Reviewed-by: Patrick Farrell <paf@cray.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>