Fix on EmagisterMemcachedExtension.php

[wibimaster]

Hi,

I think there is a little bug on file "EmagisterMemcachedExtension.php" :

Line 109 :
throw LogicException([...]
to replace by
throw new \LogicException([...]

It fix an error on my project ; I mean, it fix the error message ;)

[theUniC]

Thanks for the report!

Could you open a PR to fix this issue? Thanks! :)