Mark soap.py as deprecated

It might be removed in one of the future releases as we move away from
Twisted. Let's mark it as deprecated to make sure it won't be a
surprise.

Change-Id: Iefd69e7712d456e3bc42c3277bbfa103a2448bb6

README

@@ -8,7 +8,7 @@ depending on your python version.
 Use
 There are currently following scripts in this package:
 osmotestconfig.py - test that apps start/write with example configs
-soap.py - implementation of SOAP <-> Ctrl proxy implemented on top of Twisted
+soap.py - implementation of SOAP <-> Ctrl proxy implemented on top of Twisted (deprecated, unmaintained)
 ctrl2cgi.py - implementation of CGI <-> Ctrl proxy implemented on top of Twisted
 osmo_rate_ctr2csv.py - rate counter dumper on top of osmo_ipa
 osmo_interact_vty.py - pipe stdin/stdout to a VTY session