bsc: make perform_clear() work when VTY is not initialized

To be able to invoke perform_clear() also in tests where the VTY isn't
used, in f_logp() only access the VTY when it is actually ready.
Otherwise this causes an error and a failed test, for no good reason.

Related: OS#5337
Change-Id: I8116075f32937bd06ba14b426010bf6fec2ef402
1 file changed