fix minor bug with off by one error in max_examples tracking

Fixes a minor bug when using the max examples flag and multiple passes.  The bug probably manifests itself for things that use the pass_length variable as well, but I don't have an example of that bug.  The problem is just that the end_pass_example gets counted as an example, and probably shouldn't be.

Simple example, pre bugfix:
```
$ ../vowpalwabbit/vw -c -d train-sets/0001.dat --examples 100 --passes 10 --holdout_off
[...]
finished run
number of examples per pass = 99
passes used = 10
weighted example sum = 991
[...]
```

post bugfix:
```
$ ../vowpalwabbit/vw -c -d train-sets/0001.dat --examples 100 --passes 10 --holdout_off
[...]
finished run
number of examples per pass = 100
passes used = 10
weighted example sum = 1000
[...]
```