Move new effective_cache_size function

Previously set_default_effective_cache_size() could not handle fork,
non-fork, and bootstrap cases.

src/backend/bootstrap/bootstrap.c

@@ -312,6 +312,8 @@ AuxiliaryProcessMain(int argc, char *argv[])
 		proc_exit(1);
 	}
 
+	set_default_effective_cache_size();
+	
 	/*
 	 * Identify myself via ps
 	 */

src/backend/postmaster/postmaster.c

@@ -778,6 +778,8 @@ PostmasterMain(int argc, char *argv[])
 		ExitPostmaster(1);
 	}
 
+	set_default_effective_cache_size();
+
 	/*
 	 * Locate the proper configuration files and data directory, and read
 	 * postgresql.conf for the first time.
@@ -4476,8 +4478,6 @@ SubPostmasterMain(int argc, char *argv[])
 	memset(&port, 0, sizeof(Port));
 	read_backend_variables(argv[2], &port);
 
-	set_default_effective_cache_size();
-
 	/*
 	 * Set reference point for stack-depth checking
 	 */