doc: update the references to rally commands
doc: update the references to rally commands

Update the link to the relevant section of the Rally quick start guide
(with slightly better wording) and use the correct parameter of the
`rally verify start` command (--pattern replaced --regex long time ago).

Story: 2003099
Task: 23193
Change-Id: I2ae35e2a330ef4d10c359ae2231d7cc2b4ec2eb0

openstack/sahara-tests,openstack/sahara-tests,openstack/sahara-tests,openstack/sahara-tests,openstack/sahara-scenario,openstack/sahara-scenario,openstack/sahara-scenario