lxc: Move console checks in LXCProcessStart

https://bugzilla.redhat.com/show_bug.cgi?id=1176503

Move the two console checks - one for zero nconsoles present and the
other for an invalid console type to earlier in the processing rather than
getting after performing some setup that has to be undone for what amounts
to an invalid configuration.

This resolves the above bug since it's not not possible to have changed
the security labels when we cause the configuration check failure.

src/lxc/lxc_process.c

@@ -1050,6 +1050,20 @@ int virLXCProcessStart(virConnectPtr conn,
     }
     virCgroupFree(&selfcgroup);
 
+    if (vm->def->nconsoles == 0) {
+        virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
+                       _("At least one PTY console is required"));
+        return -1;
+    }
+
+    for (i = 0; i < vm->def->nconsoles; i++) {
+        if (vm->def->consoles[i]->source.type != VIR_DOMAIN_CHR_TYPE_PTY) {
+            virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
+                           _("Only PTY console types are supported"));
+            return -1;
+        }
+    }
+
     if (virFileMakePath(cfg->logDir) < 0) {
         virReportSystemError(errno,
                              _("Cannot create log directory '%s'"),
@@ -1149,19 +1163,8 @@ int virLXCProcessStart(virConnectPtr conn,
                                       vm->def, NULL) < 0)
         goto cleanup;
 
-    if (vm->def->nconsoles == 0) {
-        virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
-                       _("At least one PTY console is required"));
-        goto cleanup;
-    }
-
     for (i = 0; i < vm->def->nconsoles; i++) {
         char *ttyPath;
-        if (vm->def->consoles[i]->source.type != VIR_DOMAIN_CHR_TYPE_PTY) {
-            virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
-                           _("Only PTY console types are supported"));
-            goto cleanup;
-        }
 
         if (virFileOpenTty(&ttyFDs[i], &ttyPath, 1) < 0) {
             virReportSystemError(errno, "%s",