contrib/script/sip_to_pjsip: implement 'all' for allow/disallow

when 'all' is specified in an allow or disallow section, it should erase
all values from the inverse section in the default config. E.G.
allow=all should erase any deny values from default config &
vice-versa

ASTERISK-27333 #close

Change-Id: I99219478fb98f08751d769daaee0b7795118a5a6