binder_rpc_fuzzer: improve speed by reducing the no of connections

To limit the creation of socket connections,reduce the value
of kMaxConnections to 10. This will reduce the time it takes
for a socket to connect and disconnect for a large number of times.

exec/s : 68
Test: ./binder_rpc_fuzzer
Bug: 247837809

Change-Id: I23ea3e80f2c63152c00b2e7ec83d8ccb067bcf0b