dashboard - system errata - go to system's errata pane

When a user clicks the link on a system in the Applicable
Errata snippet on the dashboard, take them to the errata
pane for that system (vs the default pane).
system groups - fix from moving to asset pipeline

Update so that content view env selector is retrieved
for system groups pg.
consumer errata - ui - fix errata listing to include errata_id vs id

This commit contains a couple of small changes needed to
properly list the errata on the following pages:
- Systems -> [system] -> Content -> Errata
- System Groups -> [group] -> Content -> Errata
errata - rspec test fixes