Previously grpc++_base was dependning on grpc what caused a transitive
dependency on ssl for grpc++_unsecure. Removing the grpc dependency
shouldn't cause any issue as grpc++_base is a filegroup and all library
using it already depends on grpc directly.

This fixes https://github.com/grpc/grpc/issues/6784

This reverts commit d88e15ce.

files

This reverts commit 48d833a9, reversing
changes made to 66e9d8e8.