LU-8998 tools: parse optional argument properly

LU-8998 tools: parse optional argument properly

Use standard way '-S[opt_arg]' or '--long[=opt_arg]' to specify
optional arguments for 'lfs getstripe', the former way of parsing
optional argument is flawed.

Reverted use of '+' (at least), '-' (at most) for --component-start
and --component-end options.

Support "EOF/eof/-1" for the --component-end of 'lfs getstripe' &
'lfs find'.

Updated man pages and test scripts accordingly.

Signed-off-by: Niu Yawei <yawei.niu@intel.com>
Change-Id: I51980e9186675e3668a4b40a1edc5da6d2a1801c
Reviewed-on: https://review.whamcloud.com/26491
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Tested-by: Jenkins
Reviewed-by: Bobi Jam <bobijam@hotmail.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>