return error when  parsing conf file is failed.

issue: https://github.com/antirez/redis/issues/934

before
```c
charsyam@ubuntu:~/projects/redis-charsyam$ !s
src/redis-server redis.conf 
Segmentation fault (core dumped)
```

after
```c
*** FATAL CONFIG FILE ERROR ***
Reading the configuration file, at line 243
>>> 'requirepass 'pass'
can't parse this line
```