Problem:
Since after 5.6.7 the secure-auth option was by default set to
true from false in mysql clients. But the support for this option
was added only in mysql client. Other client tools were missing this
option and hence were resulting in the error, 
Unknown option '--secure-auth', when trying to connect to the server
Solution:
The secure-auth parameter was added to the mysql client utilities which
connect to the server i.e., Mysqldump, Mysqladmin, Mysqlcheck, Mysqlbinlog, 
MysqlImport, Mysqlslap, Mysqlshow, and also mysql_client_fw which now prevents 
the error.