Run Redfish test framework parallel on all nodes

Execute Redfish test framework tool against all target node parallel
instead of testing them one by one. This way the total execution time
does not depend on the number of nodes to be tested.

Change-Id: I2f1fbfd715aa63ccbe71e6d976404b0f21be344c
Signed-off-by: Juha Kosonen <juha.kosonen@nokia.com>