tree-wide: do not use "re" with fmemopen

The man page says nothing about "e". Glibc clearly accepts it without fuss, but
it is meaningless for a memory object (and probably doesn't work). This use is
not portable, so let's avoid it.

src/test/test-fileio.c

@@ -677,7 +677,7 @@ TEST(fgetc) {
         _cleanup_fclose_ FILE *f = NULL;
         char c;
 
-        assert_se(f = fmemopen_unlocked((void*) chars, sizeof(chars), "re"));
+        assert_se(f = fmemopen_unlocked((void*) chars, sizeof(chars), "r"));
 
         for (size_t i = 0; i < sizeof(chars); i++) {
                 assert_se(safe_fgetc(f, &c) == 1);
@@ -770,7 +770,7 @@ static void test_read_line_one_file(FILE *f) {
 TEST(read_line1) {
         _cleanup_fclose_ FILE *f = NULL;
 
-        assert_se(f = fmemopen_unlocked((void*) buffer, sizeof(buffer), "re"));
+        assert_se(f = fmemopen_unlocked((void*) buffer, sizeof(buffer), "r"));
         test_read_line_one_file(f);
 }
 

src/test/test-libmount.c

@@ -21,7 +21,7 @@ static void test_libmount_unescaping_one(
         _cleanup_(mnt_free_iterp) struct libmnt_iter *iter = NULL;
         _cleanup_fclose_ FILE *f = NULL;
 
-        f = fmemopen((char*) string, strlen(string), "re");
+        f = fmemopen((char*) string, strlen(string), "r");
         assert_se(f);
 
         assert_se(libmount_parse(title, f, &table, &iter) >= 0);