Increase tcp polling interval on data stall detection

NetworkMonitor suspects stall if we get high tcp fail rate in
10s. In a cell transition frequently environment, a certain
percentage packets lost or retransmission may stay for a longer
time interval. The shorter tcp polling interval may not able to
get confident enough result. The looser timer may also
increase validated result in the metrics which may not a good
signal. Thus, increase the polling interval to address it.

Bug: 157957111
Test: atest NetworkStackTests
Merged-In: I496a32da8f57f88908402722ebe1cd3d0a8483b6
Change-Id: I496a32da8f57f88908402722ebe1cd3d0a8483b6