fix error when make lint
fix error when make lint

```
make lint
networkdb/networkdb_test.go:88:2: should replace t.Error(fmt.Sprintf(...)) with t.Errorf(...)
networkdb/networkdb_test.go:136:2: should replace t.Error(fmt.Sprintf(...)) with t.Errorf(...)
make: *** [lint] Error 1
```

Signed-off-by: Lei Gong <701f5797ae2b6c09b5bdd061a2a20aee578496e2@alauda.io>

trebonian/docker,jimjag/docker,nalind/docker,paralin/docker,mahak/docker,konstruktoid/docker-upstream,AkihiroSuda/docker,Ramzec/docker,yosifkit/docker,trebonian/docker,bearstech/moby,thaJeztah/docker,konstruktoid/docker-upstream,thaJeztah/docker,jameszhan/docker,cpuguy83/docker,nawawi/docker,jimjag/docker,thaJeztah/docker,yosifkit/docker,trebonian/docker,docker/docker,bearstech/moby,flavio/docker,docker/docker,moby/moby,flavio/docker,moul/docker,AkihiroSuda/docker,jthelin/docker,nawawi/docker,paralin/docker,cpuguy83/docker,moul/docker,Mokolea/docker,mahak/docker,jameszhan/docker,gnailuy/docker,gnailuy/docker,djs55/docker,cpuguy83/docker,nalind/docker,cpuguy83/docker,moul/docker,paralin/docker,moby/moby,Ramzec/docker,nalind/docker,nalind/docker,AkihiroSuda/docker,moby/moby,djs55/docker,nawawi/docker,Ramzec/docker,gnailuy/docker,yosifkit/docker,moul/docker,moby/moby,docker/docker,thaJeztah/docker,Ramzec/docker,trebonian/docker,djs55/docker,paralin/docker,bearstech/moby,Mokolea/docker,vdemeester/docker,jameszhan/docker,jimjag/docker,AkihiroSuda/docker,bearstech/moby,jthelin/docker,konstruktoid/docker-upstream,gnailuy/docker,Mokolea/docker,vdemeester/docker,mahak/docker,jimjag/docker,nawawi/docker,mahak/docker,konstruktoid/docker-upstream,flavio/docker,vdemeester/docker,flavio/docker,yosifkit/docker,Mokolea/docker