Fix: Delete the used network in other namespace

[yzxiu]

fix #1635

nd: aliased to sudo nerdctl -n nerdctl-test
n: aliased to sudo nerdctl -n default

1. create network test in namespace nerdctl-test

~ nd network create test --gateway 10.10.13.1 --subnet 10.10.13.0/24
9f86d081884c7d659a2feaa0c55ad015a3bf4f1b2b0b822cd15d6c15b0f00a08

2. create container use netwrok test in namespace nerdctl-test

~ nd run -d --network test --name ndtest nginx             
b2dee527f9954e93bfa49beda122ef3f641b7bf464c02340a80d1a02462b697a

3. delete network test in namespace nerdctl-test , can't delete

~ nd network rm test                                                
ERRO[0000] network "test" is in use by container ["b2dee527f9954e93bfa49beda122ef3f641b7bf464c02340a80d1a02462b697a"]

4. fix bug

~ n network rm test                                                 
ERRO[0000] network "test" is in use by container ["b2dee527f9954e93bfa49beda122ef3f641b7bf464c02340a80d1a02462b697a"]

In addition, do we need to output the namespace of the container? like

~ n network rm test                                                 
ERRO[0000] network "test" is in use by container ["b2dee527f9954e93bfa49beda122ef3f641b7bf464c02340a80d1a02462b697a[nerdctl-test]"]

because when the output container is not in the current namespace, it may be confusing

Signed-off-by: yaozhenxiu <946666800@qq.com>

[yzxiu]

@fahedouch @AkihiroSuda PTAL

[AkihiroSuda]

Please squash commits and consider adding an integration test

[yzxiu]

Please squash commits and consider adding an integration test

done

[AkihiroSuda]

Thanks