config_save_dir may cause buffer overflow

[partimScurra]

Describe the issue
config_save_dir var is used in save_config func, where it is written into buf[128] array. Other strings that get written along with it only allow filepath to be ~90 chars long - longer filepath will result in buffer overflow.

To Reproduce
Is a code-related issue. Probably reproducible by setting config_save_dir >100 chars long.

Expected behavior
A check for the filepath size is needed to avoid overflow.

Keepalived version
2.3.4`