tests: e1inp_ipa_bsc_test: fix crash

The sequence to trigger the crash was:

1) establish a full A-bis IPA link (both OML and RSL correctly established
and ID_RESP received from BTS).
2) nc 127.0.0.1 3002 # establish OML link only

I forgot to set to NULL the oml and rsl links we're using. Otherwise,
the test calls e1inp_sign_link_destroy(rsl) which does not exists.
1 file changed