bts: don't require users to pass test case name to f_init()

The f_init() function itself can very well derive the identity using
the built-in testcasename() function.  There's no need asking users
to do that - many of them don't do it in the first place :/

Change-Id: I17a61a84fba4df31b8baab1f631c8aa55d894dbd
2 files changed