Fix irritating Enter key behaviour in container creation dialog

Pressing "Enter" in the dialog on any active form element (such as the
search input or the checkboxes) previously bubbled up to the Form, which
then activated the first popover help. This is unexpected and very
irritating especially when using the search input.

Just ignore the Enter key to fix that, similar to what the image search
modal already does.

See cockpit-project#1821 (comment)

src/ImageRunModal.jsx

@@ -744,7 +744,7 @@ export class ImageRunModal extends React.Component {
         );
 
         const defaultBody = (
-            <Form>
+            <Form onKeyDown={e => e.key === 'Enter' && e.preventDefault()}>
                 {this.state.dialogError && <ErrorNotification errorMessage={this.state.dialogError} errorDetail={this.state.dialogErrorDetail} />}
                 <FormGroup id="image-name-group" fieldId='run-image-dialog-name' label={_("Name")} className="ct-m-horizontal">
                     <TextInput id='run-image-dialog-name'

test/check-application

@@ -1738,9 +1738,16 @@ class TestApplication(testlib.MachineCase):
 
         # Local registry
         b.click('button.pf-v5-c-toggle-group__button:contains("localhost:5000")')
-        b.set_input_text("#create-image-image-select-typeahead", "my-busybox")
+        b.set_input_text("#create-image-image-select-typeahead", "my-busybox", blur=False)
         b.wait_text("button.pf-v5-c-select__menu-item:not(.pf-m-disabled)", "localhost:5000/my-busybox")
 
+        # pressing Enter does not disturb the dialog or open popup help
+        b.wait_val("#create-image-image-select-typeahead", "my-busybox")
+        b.key("Enter")
+        time.sleep(0.3)
+        self.assertFalse(b.is_present(".pf-v5-c-popover"))
+        b.wait_val("#create-image-image-select-typeahead", "my-busybox")
+
         # Select image
         b.click('button.pf-v5-c-select__menu-item:contains("localhost:5000/my-busybox")')