[key-manager] remove default master key (#5998)

When initializing, we should use randomly generated network parameters
instead of default ones, to eliminate the possibility of unintentional
use of default credentials.

tests/scripts/expect/cli-multicast-loop.exp

@@ -37,6 +37,7 @@
 source "tests/scripts/expect/_common.exp"
 
 spawn_node 1
+setup_default_network
 
 set timeout 1
 
@@ -57,6 +58,7 @@ set extaddr1 [get_extaddr]
 get_rloc16
 
 spawn_node 2 cli
+setup_default_network
 
 send "panid 0xface\n"
 expect "Done"
@@ -74,6 +76,7 @@ sleep 3
 get_rloc16
 
 spawn_node 3 cli
+setup_default_network
 
 send "panid 0xface\n"
 expect "Done"
@@ -99,6 +102,7 @@ set extaddr3 [get_extaddr]
 get_rloc16
 
 spawn_node 4 cli
+setup_default_network
 
 send "panid 0xface\n"
 expect "Done"