(MODULES-1143) Add package_manage parameter

This patch adds a package_manage parameter for both mysql::server and
mysql::client
fix dealing with empty passwords

Empty passwords ("") are passed to mysql_password("") which results in
hash: *BE1BDEC0AA74B4DCB079943E70528096CCA985F8

Expected value for password is NULL
fix: Do not hast password twice
test: Add test for creating users with empty password using mysql::db

An empty password should not be hashed.