engine should exit when it fails to obtain files exclusively

Steps to reproduce are as follows.

STR:
Load some data (say 8GB) to membase.
Kill membase using kill -9 (this is just to simulate a crash)
Restart membase.

Observed:
Memory of membase does not have persisted data.
Error message is seen in the memcache log file.
Initializing DB session from /tmp/init.sql
Executing query: ``PRAGMA journal_mode = TRUNCATE''
Executing query: ``PRAGMA locking_mode = EXCLUSIVE''
Executing query: ``PRAGMA synchronous = NORMAL''
SQLITE_BUSY (retrying)
sqlite error: database is locked
Failed to create database: unknown database kv_0

However, the process doesn't exit, so it can be hard to determine what state it is in without examining the logs. Clients would likely just receive cache misses or errors.