qemu: Fix media eject with qemu-0.12.*

In qemu-0.12.* "device '...' is locked" message was changed to "Device
..." so libvirt was no longer detecting this as an error.

bootstrap.conf

@@ -63,6 +63,7 @@ sigpipe
 snprintf
 socket
 stpcpy
+strcasestr
 strchrnul
 strndup
 strerror

src/qemu/qemu_monitor_text.c

@@ -934,7 +934,7 @@ int qemuMonitorTextEjectMedia(qemuMonitorPtr mon,
     /* If the command failed qemu prints:
      * device not found, device is locked ...
      * No message is printed on success it seems */
-    if (strstr(reply, "device ")) {
+    if (strcasestr(reply, "device ")) {
         qemuReportError(VIR_ERR_OPERATION_FAILED,
                         _("could not eject media on %s: %s"), devname, reply);
         goto cleanup;