gbproxy: don't link unnecessary

* remove sigtran include from common_vty.c because nothing uses it
* remove LIBOSMOSIGTRAN_LIBS from generic OSMO_LIBS
* remove LIBOSMOABIS_LIBS from generic OSMO_LIBS

Both LIBOSMOSIGTRAN and LIBOSMOABIS are linked explicitly when necessary
already anyway.

Change-Id: I015a9d858bc2a95f8c9a4aedd3e0a84eadcf84e1
2 files changed