We have implemented an exists() method in the DirSrv class to check wether an instance exists or not, but instead of using it, we have manual checks in a few places. Let's not repeat ourselfs and replace this code.

NOTICE:
There's this line that checks len(props) against 0 instead of 1.
https://pagure.io/lib389/blob/master/f/lib389/init.py#_922

Can this be safely replaced by a call to exists()?

Also, I replaced this:

props = self.list()
assert len(props) == 1
self.sroot = props[0][CONF_SERVER_DIR]

With this:

assert self.exists()
self.sroot = self.list()[0][CONF_SERVER_DIR]

While logically equivalent, with the second one we have 2 calls to self.list().

Thoughts on all this?