Revert "Fix output of uninitialized strings"

This reverts commit 8cf07dcbe7691dbe4f47563058659dba6ef66b05.

This is a sorry saga.

This commit:

  8e4416af45 net: Add parameter checks for VLAN clients

broken '-net socket' and this commit:

  ffad4116b9 net: Fix -net socket parameter checks

fixed the problem but introduced another problem which
this commit:

  8cf07dcbe7 Fix output of uninitialized strings

fixed that final problem, but causing us to lose some
error reporting information in the process.

Meanwhile Jan posted a patch to mostly re-do ffad4116b9
in a way that fixes the original issue, but without
losing the error reporting information. So, let's revert
8cf07dcbe7 and apply Jan's patch.

Signed-off-by: Mark McLoughlin <markmc@redhat.com>
