Fixes case of appending userdata when both template and vm data are either shellscript or cloudconfig
Fixes error when appending gzip userdata
Fixes case when userdata manual text from VM is not getting decoded-encoded correctly.
Fixes case of appending multipart data when both template and vm data contain same format types.
Refactor - moved validateUserData method to UserDataManager class
Refactor userdata test to check resultant multipart userdata thoroughly
Signed-off-by: Abhishek Kumar <abhishek.mrt22@gmail.com>