Increase a timeout that's too short

This should have been longer to start with. This oversight is due
to a poor API in TestNetworkCallback that was made that way for
backwards compatibility ; b/157405399 tracks improving this API.

Test: this
Bug: 160660082
Change-Id: If0587a2a91977427a2f679a502d838fbecdd82f2
1 file changed
tree: 913d908a31ef94f614e38fe39ff59f20e7e98765
  1. tests/