[src/Metadata.hpp] fix shadow warning

should not harm.

the fix came up while looking at the naming of the [struct Componet](https://github.com/marvin2k/tools-orogen_metadata/blob/master/src/Metadata.hpp#L24) -- which causes a warning from idl because it is a reserverd corba-keyword:

    .../base/orogen/std/.orogen/typekit/transports/corba/stdTypes.idl:24: Warning: Identifier 'Component' clashes with CORBA 3 keyword 'component'

Would _struct ComponentObject_ be a good replacement?

Signed-off-by: Martin Zenzes <martin.zenzes@dfki.de>
The code was/is perfectly valid.

Within the initialization list the variable lookup will find and assign the member-variable `value`, even if the constructor has an argument with the same name. Problem is that inside the curly-braces of the constructor the argument-variable overshadows the member-variable. So if someone later comes around and decides to change `value` inside the constructor he will change the wrong variable...

Although, now that I look at the code more closely, the variable in question is a `const&` anyways, can't be changed without special trickery... So the commit just removes a trap which is not reachable anyways.

Hmhm...