Configure Yardstick flavor to give more RAM to ARM instances

Configure Yardstick flavor to give more RAM to ARM instances

Yardstick TC005 fails with errors that indicate low memory conditions:
"fio: error while loading shared libraries:
librbd.so.1: cannot map zero-fill pages"
Changing the yardstick flavor to give 1024MB of RAM instead of 512MB
made this test case work.

JIRA: ARMBAND-275

Change-Id: I2193802082c28edb20004964d2df3780eb5eccb7
Signed-off-by: Alexandru Nemes <alexandru.nemes@enea.com>
(cherry picked from commit 5c8e38667e17059db1c62dd21f868966a6b2a519)