add missing :ref: to create link to vCenter term
add missing :ref: to create link to vCenter term

Change-Id: I6ea9a5f299be08760f20beb83f9b05d0a5b9a288

phillipsio/fuel-docs,ogelbukh/fuel-docs,ogelbukh/fuel-docs,stackforge/fuel-docs,stackforge/fuel-docs,phillipsio/fuel-docs,ogelbukh/fuel-docs,phillipsio/fuel-docs,ogelbukh/fuel-docs,phillipsio/fuel-docs