UI - Instance fails to load when DB backup directory doesn't exist

[droideck]

Issue Description
RHDS Console will fail to load an instance if the DB backup directory ( nsslapd-bakdir ) is set to a non-existing directory.
The Console will show a spinner and won't allow to select any other RHDS instances.

Steps to Reproduce
Steps to reproduce the behavior:

1. Change back up directory to non-existing one.

$ dsconf -D "cn=Directory Manager" ldap://localhost:38901 config replace nsslapd-bakdir=/DOES_NOT_EXIST
Enter password for cn=Directory Manager on ldap://localhost:38901:
Successfully replaced "nsslapd-bakdir"

2. Try to load RHDS instance.
3. Progress bar goes to 100% but instance won't load.

Expected results
Instance is loaded.