qemu: Error out if spice port autoallocation is requested, but disabled

When a user requests auto-allocation of the spice TLS port but spice TLS
is disabled in qemu.conf, we start the machine and let qemu fail instead
of erroring out sooner.

Add an error message so that this doesn't happen.

src/qemu/qemu_process.c

@@ -3292,8 +3292,14 @@ qemuProcessSPICEAllocatePorts(virQEMUDriverPtr driver,
         graphics->data.spice.port = port;
     }
 
-    if (cfg->spiceTLS &&
-        (needTLSPort || graphics->data.spice.tlsPort == -1)) {
+    if (needTLSPort || graphics->data.spice.tlsPort == -1) {
+        if (!cfg->spiceTLS) {
+            virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
+                           _("Auto allocation of spice TLS port requested "
+                             "but spice TLS is disabled in qemu.conf"));
+            goto error;
+        }
+
         if (virPortAllocatorAcquire(driver->remotePorts, &tlsPort) < 0)
             goto error;