Fix pexpect for case where pflash is not on BMC
Fix pexpect for case where pflash is not on BMC

Previously we'd hit timeout rather than failing instantly, so
modify pexpect to expect success, failure or timeout.

Signed-off-by: Stewart Smith <ec31ab75ddf977353c8f660f92ea8b23f64aef25@linux.vnet.ibm.com>

open-power/op-test-framework,open-power/op-test-framework,open-power/op-test-framework