Set fixed percentage with on the snapshot card table columns

Just for the case the description is too long, we don't want it to take
all the space.

Also add a pixel test.

Relevant to https://bugzilla.redhat.com/show_bug.cgi?id=1974200

src/components/vm/snapshots/vmSnapshotsCard.jsx

@@ -223,7 +223,7 @@ export class VmSnapshotsCard extends React.Component {
 
         detailMap = detailMap.filter(d => !d.hidden);
 
-        const columnTitles = detailMap.map(target => ({ title: target.name }));
+        const columnTitles = detailMap.map(target => ({ title: target.name, props: { width: 15 } }));
         let rows = [];
         if (vm.snapshots) {
             rows = vm.snapshots.sort((a, b) => ((b.creationTime - a.creationTime) || (a.name.localeCompare(b.name)))).map((target, snapId) => {

test/check-machines-snapshots

@@ -85,18 +85,27 @@ class TestMachinesSnapshots(VirtualMachinesCase):
         self.performAction("subVmTest1", "forceOff")
 
         time1 = datetime.now().strftime("%H:%M:%S")
-        m.execute("virsh snapshot-create-as --domain subVmTest1 --name snapshotC --description 'Description of snapshotC'")
+        long_description = "This is a long description"*10
+        m.execute("virsh snapshot-create-as --domain subVmTest1 --name snapshotC --description '{0}'".format(long_description))
 
         b.reload()  # snapshots events not available yet: https://gitlab.com/libvirt/libvirt/-/issues/44
         b.enter_page('/machines')
 
         b.wait_in_text("#vm-subVmTest1-snapshot-0-name", "snapshotC")
-        b.wait_in_text("#vm-subVmTest1-snapshot-0-description", "Description of snapshotC")
+        b.wait_in_text("#vm-subVmTest1-snapshot-0-description", long_description)
         b.wait_in_text("#vm-subVmTest1-snapshot-0-type", "shut off")
         b.wait_in_text("#vm-subVmTest1-snapshot-0-parent", "snapshotB")
         time2 = b.text("#vm-subVmTest1-snapshot-0-date")
         self.assertTrue(checkTimeDiff(time1, time2, 60))
 
+        b.assert_pixels(
+            "#vm-subVmTest1-snapshots", "vm-snapshost-card",
+            ignore=[
+                "tr:nth-child(1) .snap-creation-time",
+                "tr:nth-child(2) .snap-creation-time",
+            ]
+        )
+
     def testSnapshotCreate(self):
         b = self.browser
         m = self.machine