Telephony: Fix issue with fdn deletion

Deletion of FDN contact with name having the "=" character
fails.

If there is a contact with "=" as part of the name, then split
will result in 3strings instead of 2(key and value).

For eg: Contact name: "="

Result with current code: [string.split("=")]
string[0] = tag
string[1] = '
string[2] = '.

Expected result:
string[0] = tag (key)
string[1] = '=' (value)

If split function with 2 arguments variation is used,
this issue will be solved. Example: string.split("=", 2)

Change-Id: I6c2d6152f9b034cae9739cd96c2fe799784dc5be
Author: Jeevaka Badrappan <jeevaka.badrappan@intel.com>
Signed-off-by: Jeevaka Badrappan <jeevaka.badrappan@intel.com>
Signed-off-by: Arun Ravindran <arun.ravindran@intel.com>
Signed-off-by: Shuo Gao <shuo.gao@intel.com>
Signed-off-by: Bruce Beare <bruce.j.beare@intel.com>
Signed-off-by: Jack Ren <jack.ren@intel.com>
Author-tracking-BZ: 10805