Fix OPexpect with respect to old pexpect versions.
Fix OPexpect with respect to old pexpect versions.

>>> pexpect.__version__
'3.1'

So with pexpect 3.1 version we are getting below errors.
TypeError: __init__() got an unexpected keyword argument 'echo'

This patch fixes the issue w.r.t old pexpect package. So with this,
test suite works fine on both 3.* and 4.* series of pexpect versions.

Signed-off-by: Pridhiviraj Paidipeddi <fd8ea14509c256cbd04eaa4ee745a213945e70a1@linux.vnet.ibm.com>
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