ntdll: Return success for FSCTL_IS_VOLUME_MOUNTED ioctl.

(cherry picked from commit 0dac887f48f2067f90c4556cb5b082345b0ad403)

dlls/ntdll/file.c

diff --git a/dlls/ntdll/file.c b/dlls/ntdll/file.c
index 6e5d2a3..f6b5622 100644
--- a/dlls/ntdll/file.c
+++ b/dlls/ntdll/file.c
@@ -1491,6 +1491,7 @@
         status = RtlImpersonateSelf( SecurityImpersonation );
         break;
 
+    case FSCTL_IS_VOLUME_MOUNTED:
     case FSCTL_LOCK_VOLUME:
     case FSCTL_UNLOCK_VOLUME:
         FIXME("stub! return success - Unsupported fsctl %x (device=%x access=%x func=%x method=%x)\n",