modules/installation-bootstrap-gather: --master for each machine
modules/installation-bootstrap-gather: --master for each machine

This is what we do in CI since openshift/release@3013859bdc
(ci-operator/templates/openshift/installer/cluster-launch-installer-upi-e2e:
Gather on bootstrap failure, 2019-08-13, openshift/release#4734), so
we know it works.  Comma-delimited machines won't work, as described
in that release commit.  I'd be surprised if space-delimited worked.

vikram-redhat/openshift-docs,vikram-redhat/openshift-docs,vikram-redhat/openshift-docs,vikram-redhat/openshift-docs,vikram-redhat/openshift-docs