Update LinkProperties with MTU value

Use the MTU provided by network as part of Data Call Response.
If it is not present, use the static value from config file

Change-Id: I9d03cc9b355d09a93883fbf4ddc93fae0077641c
CRs-Fixed: 634747
Connectivity: Set TCP delayed ACK and User Configuration Flag

Provide a Mechanism to set tcp delayed ack settings from
Connectivity Service. The tcp_use_userconfig flag is set to
override the default tcp delayed ack configuration in tcp stack.
tcp_use_userconfig flag is reset when the TCP stack is required
to use default delayed ack settings. Currently the delayed ack
settings are overridden for Wifi and LTE networks only. Other
network types continue to use default delayed ack settings

Change-Id: I282ef0f6b6278b6efcef3870242974f7ee93e508
CRs-Fixed: 628139
services: change default sampling interval to -1

Change default sampling interval to -1 to avoid sampling to resolve
power consumption issue. Original implement will keep UE wake up every
12 minutes, which will cause issue when doing power standby test.

Change-Id: I018e22a44259e94bce87ceaf04ff523f035183f8