basic/env-file: also change to state PRE_KEY if we see NEWLINE in state COMMENT_ESCAPE

When we see a "\" in COMMENT state, we change the state to COMMENT_ESCAPE. When we got
a new character, we reset the state to COMMENT, but this character is not dispatched.
Usually the character is NEWLINE, if so we will stay in COMMENT state until we find
the next NEWLINE.

fix: https://github.com/systemd/systemd/issues/27975

src/test/test-env-file.c

@@ -31,9 +31,10 @@
 #define env_file_3 \
         "#SPAMD_ARGS=\"-d --socketpath=/var/lib/bulwark/spamd \\\n" \
         "#--nouser-config                                     \\\n" \
-        "normal=line                                          \\\n" \
+        "normal1=line\\\n"                                           \
+        "111\n"                                                     \
         ";normal=ignored                                      \\\n" \
-        "normal_ignored                                       \\\n" \
+        "normal2=line222\n"                                          \
         "normal ignored                                       \\\n"
 
 #define env_file_4                              \
@@ -89,7 +90,9 @@ TEST(load_env_file_3) {
 
         _cleanup_strv_free_ char **data = NULL;
         assert_se(load_env_file(NULL, name, &data) == 0);
-        assert_se(data == NULL);
+        assert_se(streq(data[0], "normal1=line111"));
+        assert_se(streq(data[1], "normal2=line222"));
+        assert_se(data[2] == NULL);
 }
 
 TEST(load_env_file_4) {