We will conditionally have a wrapper layer depending on whether the host
has the PTHREAD_SETNAME capability.  It complicates stuff.  Let's keep
the wrapper there; we opt out the pthread_setname_np() call only.

Signed-off-by: Peter Xu <peterx@redhat.com>
Message-Id: <20180412053444.17801-1-peterx@redhat.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>