LU-728 tests: pdsh HOSTLIST test suite support

For large systems it becomes tedious to list all the nodes
or devices. The application pdsh uses a HOSTLIST form to
make listing nodes more compact. This patch takes data in
the HOSTLIST format and creates a expanded list for the
shell scripts in the test suite to use. Also this gives the
option for the pdsh commands to use the nodes list in
HOSTLIST format directly. Its is also possible to use the
HOSTLIST format for devices as well as nodes.

Signed-off-by: James Simmons <uja.ornl@gmail.com>
Change-Id: Ia7a6c95ab4e701a17fc2b80d8443a5ff79da3f3c
Reviewed-on: http://review.whamcloud.com/1462
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Minh Diep <mdiep@whamcloud.com>
Reviewed-by: Yu Jian <yujian@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>