Add variables in jmstrans.sh to use directly ps command

Add variables in jmstrans.sh to use directly ps command and bypass java -version.
This pull request is backward compatibility.

- USE_JPS if true (default value) jmstrans.sh use JPS (as the actual behaviour). If not true, jmxstrans.sh use directly ps command (#89)
- CHECK_JAVA if true (default value) the java version is printed (as the actual behaviour). If not true, java is bypassed.

Bonus, if I set USE_JPS and CHECK_JAVA with false, /etc/init.d/status is faster :)

```bash
# before
time /etc/init.d/jmxtrans status
[....] Status jmxtrans: jmxtransjmxtrans is not running.
. ok 
/etc/init.d/jmxtrans status  0.37s user 0.08s system 85% cpu 0.521 total

# after
time /etc/init.d/jmxtrans status
[....] Status jmxtrans: jmxtransjmxtrans is not running.
. ok 
/etc/init.d/jmxtrans status  0.00s user 0.02s system 36% cpu 0.066 total
```

**0.066** s instead of **0.521** s.