cmd: fix golint warning

internal/container/install/install.go:19:2: a blank import should be only in a main or test package, or have a comment justifying it (golint)
	_ "github.com/google/cadvisor/cmd/internal/container/mesos/install"
	^

Signed-off-by: Kir Kolyshkin <[email protected]>

Author: kolyshkin

cmd/internal/container/install/install.go

@@ -16,6 +16,7 @@
 package install
 
 import (
+	// Register all included container providers.
 	_ "github.com/google/cadvisor/cmd/internal/container/mesos/install"
 	_ "github.com/google/cadvisor/container/containerd/install"
 	_ "github.com/google/cadvisor/container/crio/install"