LU-2043 iokit: sgpdd-survey support for multiple servers

LU-2043 iokit: sgpdd-survey support for multiple servers

This patch is an improvement to sgpdd-survey script that
allows measurement of raw storage bandwidth of multiple
servers sharing storage arrays.

Signed-off-by: Gregoire Pichon <gregoire.pichon@bull.net>
Change-Id: I2506818303ae26cc1a378f3a0da0e081582f988d
Reviewed-on: http://review.whamcloud.com/4122
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Jian Yu <jian.yu@intel.com>
Reviewed-by: Minh Diep <minh.diep@intel.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>