Ticket 48271 - Fix for self.prefix being none when SER_DEPLOYED_DIR is none https://fedorahosted.org/389/ticket/48271
Bug Description: If SER_DEPLOYED_DIR is explicitly set to None,
args.get(SER_DEPLOYED_DIR, self.prefix) is overwritten to None. This can
cause tests in 389ds and lib389 to fail immediately.
Fix Descryption The .get method is only as a fall back if args doesn't contain
the key, so this covers the case where SER_DEPLOYED_DIR is set
incorrectly to None.
Signed-off-by: Mark Reynolds <mreynolds@redhat.com>