Update xvm-prodconfig to version 1.1.56

Requested by glasgall/root@ATHENA.MIT.EDU

diff --git a/xvm-prodconfig b/xvm-prodconfig
index 5f732a4..29cecd2 160000 (submodule)
--- a/xvm-prodconfig
+++ b/xvm-prodconfig
@@ -1 +1 @@
-Subproject commit 5f732a4f4e9acc7c6b27aacb48b0e5b1d74c17df
+Subproject commit 29cecd2cfd64df86934e60f879fe3bb5fb1d14c5