values smaller than 0.001 sat/B can't be represented by CFeeRate, but they are not rejected.

```
./src/bitcoin-cli -named sendtoaddress address=bcrt1qwkmhqum095zau5rf2velq55cq938vrd7uw8m4r amount=1.23 fee_rate=0.0009

error code: -6
error message:
Fee rate (0.000 sat/vB) is lower than the minimum fee rate setting (1.000 sat/vB)
```

```
./src/bitcoin-cli -named sendtoaddress address=bcrt1qwkmhqum095zau5rf2velq55cq938vrd7uw8m4r amount=1.23 fee_rate=0.000000000009

error code: -3
error message:
Invalid amount

BOOST_CHECK(!testArgs.IsArgNegated("-bar"));
    BOOST_CHECK(testArgs.GetArg("-bar", "xxx") == "1");
    
    const char *conf_test = "nofoo=1\nfoo=1\nnobar=0\n";
    BOOST_CHECK(testArgs.ParseParameters(1, (char**)argv_test, error));
    testArgs.ReadConfigString(conf_test);
    
    
    BOOST_CHECK(!testArgs.IsArgNegated("-foo"));
    BOOST_CHECK(testArgs.GetArg("-foo", "xxx") == "1");
    
    BOOST_CHECK(!testArgs.IsArgNegated("-bar"));
    BOOST_CHECK(testArgs.GetArg("-bar", "xxx") == "1");
    
    const char *combo_test_args[] = {"ignored", "-nofoo", "-bar"};
    const char *combo_test_conf = "foo=1\nnobar=1\n";
    BOOST_CHECK(testArgs.ParseParameters(3, (char**)combo_test_args, error));
    testArgs.ReadConfigString(combo_test_conf);
    
    BOOST_CHECK(testArgs.IsArgNegated("-foo"));
    BOOST_CHECK(testArgs.GetArg("-foo", "xxx") == "0");
    BOOST_CHECK(testArgs.GetArgs("-foo").size() == 0);
    
    BOOST_CHECK(!testArgs.IsArgNegated("-bar"));
    BOOST_CHECK(testArgs.GetArg("-bar", "xxx") == "");
    BOOST_CHECK(testArgs.GetArgs("-bar").size() == 1
                && testArgs.GetArgs("-bar").front() == "");
}
BOOST_AUTO_TEST_CASE(util_ReadConfigStream)