Fix parsing of multiple IPs in --addr-pool option

[linear0211]

--addr-pool=<addr/mask> Grant wasi access to the given network addresses in
CIDR notation to the program, separated with ',',
for example:
--addr-pool=1.2.3.4/15,2.3.4.5/16

The docs say --addr-pool accepts multiple comma-separated CIDR addresses, but only the first two are currently parsed.
This changes the delimiter to , to match the documentation.

For example, using the code from samples/socket-api.

$ ./iwasm --addr-pool=1.1.1.1/32,2.2.2.2/32,0.0.0.0/15 tcp_server.wasm 
[Server] Create socket
Bind failed: Permission denied
[Server] Bind socket
[Server] Shutting down ..

[lum1n0us]

LGMT

@loganek Please help us to confirm that.