Fix the naming of _any_variable_initialized

This might be a very small issue, though the naming
`_any_variable_initalized` seems to be a typo (`initalized` -> `initialized`).
As this is
an interanl function so renaming should be safe. This fix
change the naming to `_any_variable_initialized`

Signed-off-by: Yong Tang <yong.tang.github@outlook.com>