fix pexpect.spawn.match AttributeError

Jenkins randomly throws AttributeErrors on pexpect.spawn.match, mock the
return value to fix this.

Co-Authored-By: Denis M. <dmakogon@mirantis.com>
Change-Id: I8b0ed7f8c474bedbbd60944bdd5a4119b0a6faea
Closes-Bug: #1348601
Merge "fix pexpect.spawn.match AttributeError"