Fix redundant error messages in client tools

A few client tools duplicate error messages already provided by libpq.

Discussion: https://www.postgresql.org/message-id/flat/3e937641-88a1-e697-612e-99bba4b8e5e4%40enterprisedb.com

src/bin/pg_basebackup/streamutil.c

@@ -200,8 +200,7 @@ GetConnection(void)
 
 	if (PQstatus(tmpconn) != CONNECTION_OK)
 	{
-		pg_log_error("could not connect to server: %s",
-					 PQerrorMessage(tmpconn));
+		pg_log_error("%s", PQerrorMessage(tmpconn));
 		PQfinish(tmpconn);
 		free(values);
 		free(keywords);

src/bin/pg_rewind/pg_rewind.c

@@ -282,8 +282,7 @@ main(int argc, char **argv)
 		conn = PQconnectdb(connstr_source);
 
 		if (PQstatus(conn) == CONNECTION_BAD)
-			pg_fatal("could not connect to server: %s",
-					 PQerrorMessage(conn));
+			pg_fatal("%s", PQerrorMessage(conn));
 
 		if (showprogress)
 			pg_log_info("connected to server");

src/bin/psql/startup.c

@@ -295,7 +295,7 @@ main(int argc, char *argv[])
 
 	if (PQstatus(pset.db) == CONNECTION_BAD)
 	{
-		pg_log_error("could not connect to server: %s", PQerrorMessage(pset.db));
+		pg_log_error("%s", PQerrorMessage(pset.db));
 		PQfinish(pset.db);
 		exit(EXIT_BADCONN);
 	}