Changed dummy regex (in perfmon) to one that cannot match anything.

Signed-off-by: Thomas Sanders <thomas.sanders@citrix.com>
CP-2190 for PR-1221: performance alert for host sr througput

Added perfmon defaults for "sr_io_throughput_total_xxxxxxxx" alert
for throughput on the SR whose uuid starts with xxxxxxxx.
(Second of two parts of CP-2190)

Signed-off-by: Thomas Sanders <thomas.sanders@citrix.com>