Lessen library-loading log level.

Previously, messages were emitted at the LOG level every time a
backend preloaded a library. That was acceptable (though unnecessary)
for shared_preload_libraries; but it was excessive for
local_preload_libraries and session_preload_libraries. Reduce to
DEBUG1.

Also, there was logic in the EXEC_BACKEND case to avoid repeated
messages for shared_preload_libraries by demoting them to
DEBUG2. DEBUG1 seems more appropriate there, as well, so eliminate
that special case.

Peter Geoghegan.

src/backend/utils/init/miscinit.c

@@ -1240,7 +1240,6 @@ load_libraries(const char *libraries, const char *gucname, bool restricted)
 {
 	char	   *rawstring;
 	List	   *elemlist;
-	int			elevel;
 	ListCell   *l;
 
 	if (libraries == NULL || libraries[0] == '\0')
@@ -1262,18 +1261,6 @@ load_libraries(const char *libraries, const char *gucname, bool restricted)
 		return;
 	}
 
-	/*
-	 * Choose notice level: avoid repeat messages when re-loading a library
-	 * that was preloaded into the postmaster.	(Only possible in EXEC_BACKEND
-	 * configurations)
-	 */
-#ifdef EXEC_BACKEND
-	if (IsUnderPostmaster && process_shared_preload_libraries_in_progress)
-		elevel = DEBUG2;
-	else
-#endif
-		elevel = LOG;
-
 	foreach(l, elemlist)
 	{
 		char	   *tok = (char *) lfirst(l);
@@ -1291,7 +1278,7 @@ load_libraries(const char *libraries, const char *gucname, bool restricted)
 			filename = expanded;
 		}
 		load_file(filename, restricted);
-		ereport(elevel,
+		ereport(DEBUG1,
 				(errmsg("loaded library \"%s\"", filename)));
 		pfree(filename);
 	}