Remove redundant lt_dlerror() calls

The redundant lt_dlerror() calls were taken from the examples to clean
any previous errors from lt_dl...() calls.  However upon code
inspection, it was discovered there are no such paths that could cause
the lt_dlerror() to return spurious error messages.

bin/named/unix/dlz_dlopen_driver.c

@@ -193,8 +193,7 @@ dl_load_symbol(dlopen_data_t *cd, const char *symbol, bool mandatory) {
 				   cd->dl_path, symbol, errmsg);
 		}
 	}
-	/* Cleanup any errors */
-	(void)lt_dlerror();
+
 	return (ptr);
 }
 
@@ -243,8 +242,6 @@ dlopen_dlz_create(const char *dlzname, unsigned int argc, char *argv[],
 		goto failed;
 	}
 
-	(void)lt_dlerror();
-
 	/* Find the symbols */
 	cd->dlz_version =
 		(dlz_dlopen_version_t *)dl_load_symbol(cd, "dlz_version", true);

lib/dns/dyndb.c

@@ -99,7 +99,6 @@ load_symbol(lt_dlhandle handle, const char *filename, const char *symbol_name,
 			      symbol_name, filename, errmsg);
 		return (ISC_R_FAILURE);
 	}
-	(void)lt_dlerror();
 
 	*symbolp = symbol;
 
@@ -132,9 +131,6 @@ load_library(isc_mem_t *mctx, const char *filename, const char *instname,
 		CHECK(ISC_R_FAILURE);
 	}
 
-	/* Clear dlerror */
-	(void)lt_dlerror();
-
 	CHECK(load_symbol(handle, filename, "dyndb_version",
 			  (void **)&version_func));
 

lib/ns/hooks.c

@@ -98,14 +98,6 @@ load_symbol(void *handle, const char *modpath, const char *symbol_name,
 	REQUIRE(handle != NULL);
 	REQUIRE(symbolp != NULL && *symbolp == NULL);
 
-	/*
-	 * Clear any pre-existing error conditions before running dlsym().
-	 * (In this case, we expect dlsym() to return non-NULL values
-	 * and will always return an error if it returns NULL, but
-	 * this ensures that we'll report the correct error condition
-	 * if there is one.)
-	 */
-	lt_dlerror();
 	symbol = lt_dlsym(handle, symbol_name);
 	if (symbol == NULL) {
 		const char *errmsg = lt_dlerror();