LU-9680 utils: new llapi_param_display_value().

LU-9680 utils: new llapi_param_display_value().

Currently the special YAML handling is done in lustre_cfg.c
for param handling. Other functionality internal to
liblustreapi.so will use this as well so move the handling
internal to liblustreapi.so. Currently we only make the new
llapi_param_display_value() function visible only to the
liblustreapi internal code. Later when we support /sys access
we can make this available for general use.

The "lctl get_param" and "lctl list_param" generally worked
for non-root users, but not for parameters under
/sys/kernel/debug due to permission changes in the kernel.
We still lacked proper non-root access for lctl get_param and
lctl list_param. Implement full lctl get_param functionality
for non-root users. Also make lctl list_param work for
non-root users. These changes will also work with any
parameters implemented with Netlink.

Change-Id: Ifd9aad16decb0803a336314d4dea38664ff41aa4
Signed-off-by: James Simmons <jsimmons@infradead.org>
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/49491
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Jian Yu <yujian@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>