Update plugin-manager submodule to the latest master

The submodule update includes the following commits:

00e5794 Fix loading of core plugins on Windows

Change-Id: Icf39812b65a430a9500d56375dce3361d009b16d
diff --git a/plugins/plugin-manager b/plugins/plugin-manager
index d6a3381..00e5794 160000
--- a/plugins/plugin-manager
+++ b/plugins/plugin-manager
@@ -1 +1 @@
-Subproject commit d6a33818440eb20aca64a761f79652525b3eb060
+Subproject commit 00e57948f4f112c226028bc5c8d8fe60f770038f