dist/debian: skip stripping libprotobuf.so.15
dist/debian: skip stripping libprotobuf.so.15

dh_strip won't able to strip libprotobuf.so.15, and we actually don't
need to strip dependency libraries, so skip it.

Fixes #4135

Signed-off-by: Takuya ASADA <4ebfb6f510af412d6e89fefa3ab96d9c8b5e3fff@scylladb.com>
Message-Id: <20190123202213.2117-4-4ebfb6f510af412d6e89fefa3ab96d9c8b5e3fff@scylladb.com>

scylladb/scylla,scylladb/scylla,scylladb/scylla,avikivity/scylla,avikivity/scylla,scylladb/scylla,avikivity/scylla