test: Use grep -E instead of egrep

The latter has been deprecated.

Author: jpgrayson

t/test-lib-functions.sh

@@ -867,7 +867,7 @@ test_path_exists () {
 test_dir_is_empty () {
 	test "$#" -ne 1 && BUG "1 param"
 	test_path_is_dir "$1" &&
-	if test -n "$(ls -a1 "$1" | egrep -v '^\.\.?$')"
+	if test -n "$(ls -a1 "$1" | grep -E -v '^\.\.?$')"
 	then
 		echo "Directory '$1' is not empty, it contains:"
 		ls -la "$1"