vty: add 'gsmtap-sapi (enable-all|disable-all)' command
vty: add 'gsmtap-sapi (enable-all|disable-all)' command

It's more convenient to use one command to enable/disable sending
of all kinds of UL/DL messages at once, rather than specifying
all of them individually.

Adjust config_write_bts_single(), so it would not print unknown
GSMTAP SAPI entries if gsmtap_sapi_mask is set to UINT32_MAX.

Change-Id: Icd7fce860ecdcf8ffa107bdfee7ec94ea9ea6cb2

osmocom/osmo-bts,osmocom/osmo-bts,osmocom/osmo-bts