Cisco: unsupported format character in log format

CiscoCfgAgent.hosting_devices_removed() contains an error in the
format string used to log errors:

    LOG.error(_LE("Invalid payload format for received RPC message "
		"`hosting_devices_removed`. Error is %{error}s. "
		"Payload is %(payload)s"),
	      {'error': e, 'payload': payload})

"%{error}s" should be "%(error)s"

The existing version raises "ValueError: unsupported format character
'{' (0x7b)" when invoked.

(found via pylint)

Change-Id: Ic5e9db2a19aa7652cbbd1ee04d7e02914e8d0093
Closes-Bug: #1403304
Merge "Cisco: unsupported format character in log format"