plugin: fix empty-lines (revive)

plugin/v2/settable_test.go:24:29: empty-lines: extra empty line at the end of a block (revive)
    plugin/manager_linux.go:96:6: empty-lines: extra empty line at the end of a block (revive)
    plugin/backend_linux.go:373:16: empty-lines: extra empty line at the start of a block (revive)

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
(cherry picked from commit 4eb9b5f20e)
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

plugin/backend_linux.go

@@ -370,7 +370,6 @@ func (pm *Manager) Push(ctx context.Context, name string, metaHeader http.Header
 
 	pusher, err := resolver.Pusher(ctx, ref.String())
 	if err != nil {
-
 		return errors.Wrap(err, "error creating plugin pusher")
 	}
 

plugin/manager_linux.go

@@ -112,7 +112,6 @@ func (pm *Manager) pluginPostStart(p *v2.Plugin, c *controller) error {
 			shutdownPlugin(p, c.exitChan, pm.executor)
 			return err
 		}
-
 	}
 	pm.config.Store.SetState(p, true)
 	pm.config.Store.CallHandler(p)

plugin/v2/settable_test.go

@@ -38,7 +38,6 @@ func TestNewSettable(t *testing.T) {
 		if s.value != c.value {
 			t.Fatalf("expected value to be %q, got %q", c.value, s.value)
 		}
-
 	}
 }