3 issues found by SonarQube

[lorddev]

See screenshot

[LordVeovis]

I have fixed the lock issue. The GetHashCode however seems good to me even if the XmlRpcDateTime is a class and not a struct, to have a consistent behavior with System.DateTime

[lorddev]

Non-flags enum marked as [Flags] in XmlRpcNonStandard.

[lorddev]

The flags enum is used for flags, so I don't know why it's reporting this. I would not change it.

[epgeroy]

I set the flag to AllowStringFaultCode and it keeps throwing the error Exception thrown: 'CookComputing.XmlRpc.XmlRpcTypeMismatchException' in Kveer.XmlRPC.dll: 'fault response contains string value where integer expected [fault response : struct mapped to type Fault : member faultCode mapped to type Int32]'