rpcrt4: Don't abort reading from a pipe if a single read is short.

dlls/rpcrt4/rpc_transport.c

diff --git a/dlls/rpcrt4/rpc_transport.c b/dlls/rpcrt4/rpc_transport.c
index 1e759a6..367ca35 100644
--- a/dlls/rpcrt4/rpc_transport.c
+++ b/dlls/rpcrt4/rpc_transport.c
@@ -382,6 +382,8 @@
   {
     DWORD bytes_read;
     ret = ReadFile(npc->pipe, buf, bytes_left, &bytes_read, NULL);
+    if (!ret && GetLastError() == ERROR_MORE_DATA)
+        ret = TRUE;
     if (!ret || !bytes_read)
         break;
     bytes_left -= bytes_read;