RDKCOM-1077 WPS ConfigMethodsEnabled is returning EMPTY when wrong values ...
RDKCOM-1077 WPS ConfigMethodsEnabled is returning EMPTY when wrong values ...

Reason For Change:
When we set  WPS ConfigMethodsEnabled with some junk data, the existing config methods get nullified. Instead it would say CCSP_ERR_INVALID_PARAMETER_VALUE.
Updated code to return FALSE when it is setting junk or existing method.
Also added extra check to wipe out exiting methods i.e. when pass NONE in set command , ConfigMethodsEnabled will become empty.
Test Procedure:
1. dmcli eRT getv Device.WiFi.AccessPoint.1.WPS.ConfigMethodsEnabled
  Verify that PushButton,PIN gets returned.
2. dmcli eRT setv Device.WiFi.AccessPoint.1.WPS.ConfigMethodsEnabled string "NONE"
   Verify that it returns EMPTY string.
3.dmcli eRT setv Device.WiFi.AccessPoint.1.WPS.ConfigMethodsEnabled string "PushButton,PIN"
    Verify that it returns  PushButton,PIN
4. dmcli eRT setv Device.WiFi.AccessPoint.1.WPS.ConfigMethodsEnabled string junk
  should return  CCSP_ERR_INVALID_PARAMETER_VALUE(9007)
Risks: None
Signed-off-by: chandra Sekhar N <csekha.contractor@libertyglobal.com>

Reason for change:  WPS ConfigMethodsEnabled is returning EMPTY when wrong values ...

(cherry picked from commit 3a39da9df138f2c21800224156ce61b1f0ed7773)

Change-Id: I9e84ef23125de9607c536700b81319165905be28

rdkcmf/rdkb-CcspWifiAgent,rdkcmf/rdkb-CcspWifiAgent,rdkcmf/rdkb-CcspWifiAgent