LU-4783 mgs: start params log during mgs initialization

LU-4783 mgs: start params log during mgs initialization

Params log was introduced by LU-3155 to set parameters permanently
with lctl "set_param -P" instead of "conf_param". But in a newly
mounted filesystem, the log won't be created automatically until "lctl
set_param -P" is called. This causes that the other servers can't make
a local copy successfully during their setup, and the misleading
console error message "LustreError: 13a-8: Failed to get MGS log
params and no local copy." is printed.
This patch is to start params log during mgs intialization so that the
error message is quieted.
Also, test_76b is added to conf-sanity.sh to verify params log setup.

Signed-off-by: Emoly Liu <emoly.liu@intel.com>
Change-Id: Ifc3abc1e35ef20230a1be1cdf1c4cc8f57b2788e
Reviewed-on: http://review.whamcloud.com/9737
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Mike Pershin <mike.pershin@intel.com>
Reviewed-by: Fan Yong <fan.yong@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>