smoketest: remove base accel-ppp testcase function comments

Python unittest framework treads the comments as test names during execution:

Example:
test_accel_ipv4_pool (__main__.TestVPNPPTPServer.test_accel_ipv4_pool)
Test accel-ppp IPv4 pool ... ok

(cherry picked from commit e9883143310993d87ba2e0c8ec7ef3b9faf928b1)