mis-assigned keyword arguments when two function parameters have the same name

### Environment
Python 3.9.2
`fire==0.4.0`

### Example Script
I have the following example `script.py`:

```python
import fire

class Foo:
def __init__(self):
print("__init__")

def bar(self, param=0):
print(f"bar (param={param})")
return self

def baz(self, param=0):
print(f"baz (param={param})")
return self

def end(self):
return "end"

if __name__ == "__main__":
fire.Fire(Foo)
```

### Example Usages (which demonstrate a problem)

When I use the script and provide the arguments by *position*, it works fine:

```
$ python script.py bar 3 baz 5 end
__init__
bar (param=3)
baz (param=5)
end
```

But when I provide the arguments by *keyword*, the output is different and the program brings up the command-line help text for `Foo`:

```
$ python script.py bar --param=3 baz --param=5 end
__init__
bar (param=5)
baz (param=end)
```

More examples:

```
$ python script.py bar --param=3 baz 5 end
__init__
bar (param=3)
baz (param=5)
end
```

```
$ python script.py bar 3 baz --param=5 end
__init__
bar (param=5)
ERROR: Could not consume arg: 3
Usage: fire_issue_eg.py bar 3
available commands: bar | baz | end

For detailed information on this command, run:
fire_issue_eg.py bar 3 --help
```

### Thoughts

It looks like there is a problem:
- when Fire is running through two (or more) callable objects, and each object has an identically-named parameter (in the above example, `param`)
- when that parameter is provided on the command line via keyword on the 2nd(+) function called (in this example, `baz`)