dissolve libcommon: move talloc ctx into msc_main.c, drop talloc_ctx.c

Drop tall_bsc_ctx; in mncc_sock_init(), talloc the mncc_sock_state from
gsm_network.

In tests or utils, move from using an extern tall_bsc_ctx to a local root
context pointer.

Change-Id: I92c252be1d1e7634f1653de47d37c99d77d9501c
10 files changed