tests: update spread test for unknown plug/slot with snapctl is-connected

[stolowski]

Update snapctl is-connected spread test to check new error introduced with #9168 (will fail until that PR lands).

[sergiocazzolato]

@stolowski, thanks for the update

The test is failing on debian with this:

++ test-snap.checkconn home

• OUT=
• MATCH 'error running snapctl: snap "test-snap" has no plug or slot named "home"'
• echo ''
  grep error: pattern not found, got:

---

[sergiocazzolato]

Also saw this in fedora:

++ test-snap.checkconn home

• OUT='WARNING: cgroup v2 is not fully supported yet, proceeding with partial confinement'
• MATCH 'error running snapctl: snap "test-snap" has no plug or slot named "home"'
• echo 'WARNING: cgroup v2 is not fully supported yet, proceeding with partial confinement'
  grep error: pattern not found, got:
  WARNING: cgroup v2 is not fully supported yet, proceeding with partial confinement

---

[stolowski]

@stolowski, thanks for the update

The test is failing on debian with this:

As mentioned in the description failures were expected until the prerequisite lands; this just happened and I merged master, let's see how it goes now.