test: Drop existing podman images

Our Fedora/RHEL CI images have the cockpit/base and the underlying
fedora container image, but the Debian image does not. Avoid the
ambiguity by cleaning up all existing images in vm.install.

Closes cockpit-project#466

test/check-application

@@ -155,11 +155,11 @@ class TestApplication(testlib.MachineCase):
 
         # Test owner filtering
         if auth:
-            b.wait_js_func("ph_count_check", "#containers-images tbody", 8)
+            b.wait_js_func("ph_count_check", "#containers-images tbody", 6)
             b.wait_js_func("ph_count_check", "#containers-containers tbody", 2)
 
             b.set_val("#containers-containers-owner", "system")
-            b.wait_js_func("ph_count_check", "#containers-images tbody", 5)
+            b.wait_js_func("ph_count_check", "#containers-images tbody", 3)
             b.wait_in_text("#containers-images", "system")
             b.wait_js_func("ph_count_check", "#containers-containers tbody", 1)
             b.wait_in_text("#containers-containers", "system")
@@ -171,7 +171,7 @@ class TestApplication(testlib.MachineCase):
             b.wait_in_text("#containers-containers", "admin")
 
             b.set_val("#containers-containers-owner", "all")
-            b.wait_js_func("ph_count_check", "#containers-images tbody", 8)
+            b.wait_js_func("ph_count_check", "#containers-images tbody", 6)
             b.wait_js_func("ph_count_check", "#containers-containers tbody", 2)
         else: # No 'owner' selector when not privileged
             b.wait_not_present("#containers-containers-owner")
@@ -435,7 +435,7 @@ class TestApplication(testlib.MachineCase):
             # `User Service is also available` banner should not be present
             b.wait_not_present("#overview div.pf-c-alert")
             # There should not be any duplicate images listed
-            b.wait_js_func("ph_count_check", "#containers-images tbody", 3)
+            b.wait_js_func("ph_count_check", "#containers-images tbody", 1)
             # There should not be 'owner' selector
             b.wait_not_present("#containers-containers-owner")
 

test/vm.install

@@ -55,6 +55,7 @@ if type firewall-cmd >/dev/null 2>&1; then
 fi
 
 # grab a few images to play with; tests run offline, so they cannot download images
+podman rmi --all
 podman pull docker.io/busybox
 podman pull docker.io/alpine
 podman pull docker.io/registry:2
@@ -63,6 +64,7 @@ podman pull docker.io/registry:2
 loginctl enable-linger $(id -u admin)
 sudo -i -u admin bash << EOF
 systemctl --user disable --now systemd-tmpfiles-clean.timer
+podman rmi --all
 podman pull docker.io/busybox
 podman pull docker.io/alpine
 podman pull docker.io/registry:2