MasterKeyConfiguration class has the password in Properties

[Niranjan-K]

In the MasterKeyConfiguration class, the password in the master key yaml file, is read and stored in a properties object. This file should be read as an inputstream and the password should be stored in the char array.

[vidurananayakkara]

@Niranjan-K This issue is now relevant to the Carbon SecVault repository since it is moved out from Carbon Kernel. Could you please move this issue to the Carbon SecVault Repo

[jsdjayanga]

Created a new issue in secure vault repo
wso2/carbon-secvault#22