`pt-fingerprint --query` returns non-zero on success

[Jordan Raine]

When running pt-fingerprint with a single query using the --query option, the exit status is 1 instead of 0.

```
$ pt-fingerprint --query "SELECT * FROM users WHERE id = 1"
select * from users where id = ?
$ echo $?
1
```

This is not the case when the query is piped to the command:

```
$ echo "SELECT * FROM users WHERE id = 1" | pt-fingerprint
select * from users where id = ?
$ echo $?
0
```

Additional information:

```
$ pt-fingerprint --version
pt-fingerprint 2.2.16
$ mysql --version
mysql Ver 14.14 Distrib 5.6.24-72.2, for osx10.10 (x86_64) using EditLine wrappe
```

There was no output to STDERR.

[Shahriyar Rzayev (rzayev-sehriyar)]

Percona now uses JIRA for bug reports so this bug report is migrated to: https://jira.percona.com/browse/PT-1348