Bump minimum default RAM for Ironic nodes to 1GB

Set the default RAM for Ironic BM VMs to 1GB to ensure DIB produced deployment
ramdisks function correctly across older and newer kernels, regardless of
rootfstype.

Change-Id: Ifc15a4430aa63c3599e7fd76f5116dc7b728ead0
Closes-bug: #1311987
Remove lib/tempest errexit handling

lib/tempest had code to set -o errexit and restore the setting after
configure_tempest had run. This code didn't work, but it is no longer
necessary since we set errexit for all of devstack (see change 88521;
Change-Id Ia477e04567046a7fcdedf699423165bc577b72ad).

This changeset removes the errexit handling code from lib/tempest.

Change-Id: I2b0bc3c55a5d9bbb688f1e2e8e0fe133830a4172
Merge "Remove lib/tempest errexit handling"
Merge "Bump minimum default RAM for Ironic nodes to 1GB"