add osmo_fsm_inst_update_id_f()

In the osmo-msc, I would like to set the subscr conn FSM identifier by a string
format, to include the type of Complete Layer 3 that is taking place. I could
each time talloc a string and free it again. This API is more convenient.

From osmo_fsm_inst_update_id(), call osmo_fsm_inst_update_id_f() with "%s" (or
pass NULL).

Put the name updating into separate static update_name() function to clarify.

Adjust the error message for erratic ID: don't say "allocate", it might be from
an update. Adjust test expectation.

Change-Id: I76743a7642f2449fd33350691ac8ebbf4400371d

0 files changed, 0 insertions, 0 deletions