Ignore errors in RedisConnectionPool destructor

Ignore errors in RedisConnectionPool destructor

The destructor can be called on shutdown so any operation which
relies on another object or resource can fail. E.g. running
anything involving Redis (such as >>new Message('').''<<)
from shell.php and then exiting will result in a RedisException
since the PHP engine closes the Redis connection before destroying
the connection pool. Such errors can be safely ignored.

Change-Id: I38474a9dda89c82edbcb878facb4a97740e9189a