mux create: do not update mux parameters from multiple origin muxes (nit)

NIT data:

mux: '12109H' : dvb-s2 pos 235E freq 12129000 V sym 275000 fec 2/3 mod 8PSK roff 20
mux: '11739V' : dvb-s2 pos 235E freq 12129000 V sym 275000 fec 2/3 mod 8PSK roff 25

This change avoids the frequent automatic parameter changes using
the origin (first hit) mux which broadcasted the data. The origin
mux is locked for 24 hours from the last update.