Fix usagetype parameter autocomplete

[hsato03]

Currently, when using autocomplete in the usagetype parameter (present in APIs such as quotaPresetVariableList and quotaCreateTariff) the CLI panics.

$ cmk  
Apache CloudStack 🐵 CloudMonkey 6.4.0
Report issues: https://github.com/apache/cloudstack-cloudmonkey/issues

panic: interface conversion: interface {} is float64, not string

goroutine 36 [running]:
github.com/apache/cloudstack-cloudmonkey/cli.buildArgOptions(0xc000f48000?, 0x0)
	/Users/rohit/lab/apache/cloudstack-cloudmonkey/cli/completer.go:126 +0x8c5
github.com/apache/cloudstack-cloudmonkey/cli.(*autoCompleter).Do(0xc00004f790, {0xc000e9e3f0, 0x0?, 0x24}, 0x24)
	/Users/rohit/lab/apache/cloudstack-cloudmonkey/cli/completer.go:402 +0x136c
github.com/chzyer/readline.(*opCompleter).OnComplete(0xc000130ee0)
	/Users/rohit/lab/apache/cloudstack-cloudmonkey/vendor/github.com/chzyer/readline/complete.go:101 +0x10d
github.com/chzyer/readline.(*Operation).ioloop(0xc000130e00)
	/Users/rohit/lab/apache/cloudstack-cloudmonkey/vendor/github.com/chzyer/readline/operation.go:180 +0xc8a
created by github.com/chzyer/readline.NewOperation in goroutine 1
	/Users/rohit/lab/apache/cloudstack-cloudmonkey/vendor/github.com/chzyer/readline/operation.go:88 +0x2d6

This PR aims to fix this bug and allow users to use the completer for the usagetype parameter.