Wait for criuProcess once

[tedyu]

In linuxContainer#criuSwrk(), the deferred func may wait on criuProcess for a second time, if the following has been executed (around line 1640):

	st, err = criuProcess.Wait()

This PR adds check for st so that there is no redundant wait.

Note: there is already deferred criuClientCon.Close() on line 1476

[kolyshkin]

1. I do not understand the meaning of

                if err != nil {
                        return
                }

in the defer func(). Looks like it does nothing, so it does not make sense to have it at all (unless I am mistaken and it actually means something).

2. Since we are ignoring the error, there is nothing wrong to call Wait for a second time.

3. I would remove the second "criuClientCon.Close()" (as a separate patch, first in the series).

[kolyshkin]

@avagin PTAL

[tedyu]

w.r.t. #1, I have updated the PR to log the error.

[tedyu]

Ping @avagin

[avagin]

LGTM

[kolyshkin]

LGTM

[kolyshkin]

@AkihiroSuda @mrunalp PTAL

[kolyshkin]

LGTM

[mrunalp]

LGTM