Roll back transaction if execution of proc fails

This change to the code the executes stored procedures should abort the transaction if execution of a stored procedure fails.  I need to figure out how to test this, since it will affect all of AG and *not* just the labadmin site...
Positive

```python
11:57:58 (mcdonadt@rl1-1-220-168-dhcp):/Users/mcdonadt/ResearchWork/software/American-Gut/americangut
> def foo(thing):
    try:
        float(thing)
    except:
        print "Excepted"
    else:
        return "hit return"
    finally:
        print "hit finally"
   ...:

11:58:15 (mcdonadt@rl1-1-220-168-dhcp):/Users/mcdonadt/ResearchWork/software/American-Gut/americangut
> foo("asd")
Excepted
hit finally

11:58:18 (mcdonadt@rl1-1-220-168-dhcp):/Users/mcdonadt/ResearchWork/software/American-Gut/americangut
> foo("123")
hit finally
Out[5]: 'hit return'
```