Move virGetUserEnt() to where its needed

In the first if case, virGetUserEnt() isn't necessary so don't bother
calling it before determining we need it.

src/util/virutil.c

@@ -759,12 +759,13 @@ static char *virGetXDGDirectory(const char *xdgenvname, const char *xdgdefdir)
 {
     const char *path = getenv(xdgenvname);
     char *ret = NULL;
-    char *home = virGetUserEnt(geteuid(), VIR_USER_ENT_DIRECTORY);
+    char *home = NULL;
 
     if (path && path[0]) {
         if (virAsprintf(&ret, "%s/libvirt", path) < 0)
             goto no_memory;
     } else {
+        home = virGetUserEnt(geteuid(), VIR_USER_ENT_DIRECTORY);
         if (virAsprintf(&ret, "%s/%s/libvirt", home, xdgdefdir) < 0)
             goto no_memory;
     }