main, tests: use msgb_talloc_ctx_init() (new)

msgb_set_talloc_ctx() is deprecated since libosmocore commit
f45334be29016a36594aacc07c90e262e4994525 / change-id
I747fbbf977c4d2c868c8dead64cfc5fd86eb8d4c

Change-Id: I8d40abec428b739460ed545c9983d1b63021bd08
6 files changed