Move initLibStore() immediately after initLibUtil()

Part of an effort to make it easier to initialize the right things,
by moving code into the appropriate libraries.

The goal of this reordering is to make initLibStore self-sufficient
in a following commit.

src/libmain/shared.cc

@@ -162,6 +162,7 @@ void initNix()
 #endif
 
     initLibUtil();
+    initLibStore();
 
     if (sodium_init() == -1)
         throw Error("could not initialise libsodium");
@@ -223,7 +224,6 @@ void initNix()
 #endif
 
     preloadNSS();
-    initLibStore();
 }