Increase the DNS TTL to 5s to fix netd_test.

Under some rare, but repeatable, conditions, the cache would expire
before the second getaddrinfo() call in the test was executed, thus causing
superfluous queries that made the test fail. Increasing the TTL fixes
this.

BUG: 28252032

Change-Id: I82919c147ca9c1b7a92f963556b27fb72e3d2222