Remove useless shared in ServiceManager

Shared or not a service as no sense, because a service shared is
register in "instances" array, and "setService" register automatically
in "instances" array. With "setService", all is always shared !
Revert unrelated changes
Merge branch 'hotfix/remove-useless-shared-service-manager' of git://github.com/blanchonvincent/zf2 into hotfix/3663
Merge branch 'hotfix/3663'

Close #3663