qemuDomainBuildNamespace: Handle special file mount points

https://bugzilla.redhat.com/show_bug.cgi?id=1459592

In 290a00e4 I've tried to fix the process of building a
qemu namespace when dealing with file mount points. What I
haven't realized then is that we might be dealing not with just
regular files but also special files (like sockets). Indeed, try
the following:

1) socat unix-listen:/tmp/soket stdio
2) touch /dev/socket
3) mount --bind /tmp/socket /dev/socket
4) virsh start anyDomain

Problem with my previous approach is that I wasn't creating the
temporary location (where mount points under /dev are moved) for
anything but directories and regular files.
Signed-off-by: NMichal Privoznik <mprivozn@redhat.com>
Reviewed-by: NJohn Ferlan <jferlan@redhat.com>

src/qemu/qemu_domain.c

@@ -8357,9 +8357,11 @@ qemuDomainBuildNamespace(virQEMUDriverConfigPtr cfg,
             goto cleanup;
         }
 
-        /* At this point, devMountsPath is either a regular file or a directory. */
+        /* At this point, devMountsPath is either:
+         * a file (regular or special), or
+         * a directory. */
         if ((S_ISDIR(sb.st_mode) && virFileMakePath(devMountsSavePath[i]) < 0) ||
-            (S_ISREG(sb.st_mode) && virFileTouch(devMountsSavePath[i], sb.st_mode) < 0)) {
+            (!S_ISDIR(sb.st_mode) && virFileTouch(devMountsSavePath[i], sb.st_mode) < 0)) {
             virReportSystemError(errno,
                                  _("Failed to create %s"),
                                  devMountsSavePath[i]);