make test: relax BFD time intervals

Increased time intervals mean longer test runs, but also reduce
the chance of getting annoying (especially in gerrit) random failures.
Now that tests are split into `basic' and `all', the increased runtime
of BFD tests (of which majority doesn't run in basic case) doesn't
matter too much..

Change-Id: I4a15bb4facad634f123bc9cc6f45eddbf4976fd1
Signed-off-by: Klement Sekera <ksekera@cisco.com>