Fix a bug which prevented creating new users on mysql 5.7.6+ servers …

…(introduced while fixing #2418) (see also #2229)

Source/SPUserManager.m

@@ -1078,10 +1078,21 @@ - (BOOL)insertUser:(SPUserMO *)user
		
		NSString *idString;
		if(requiresPost576PasswordHandling) {
			//copy the hash from the parent. if the parent password changes at the same time, updateUser: will take care of it afterwards
			NSString *plugin = [[[user parent] valueForKey:@"plugin"] tickQuotedString];
			NSString *hash = [[[user parent] valueForKey:@"authentication_string"] tickQuotedString];
			idString = [NSString stringWithFormat:@"IDENTIFIED WITH %@ AS %@",plugin,hash];
			// there are three situations to cover here:
			//   1) host added, parent user unchanged
			//   2) host added, parent user password changed
			//   3) host added, parent user is new
			if([[user parent] valueForKey:@"originaluser"]) {
				// 1 & 2: If the parent user already exists we always use the old password hash. if the parent password changes at the same time, updateUser: will take care of it afterwards
				NSString *plugin = [[[user parent] valueForKey:@"plugin"] tickQuotedString];
				NSString *hash = [[[user parent] valueForKey:@"authentication_string"] tickQuotedString];
				idString = [NSString stringWithFormat:@"IDENTIFIED WITH %@ AS %@",plugin,hash];
			}
			else {
				// 3: If the user is new, we take the plaintext password value from the UI
				NSString *password = [[[user parent] valueForKey:@"password"] tickQuotedString];
				idString = [NSString stringWithFormat:@"IDENTIFIED BY %@",password];
			}
		}
		else {
			BOOL passwordIsHash;