Remove residual package

Because we define clients as library before, this admin package's
all contents are moved to other places. This package is
unnecessary, so delete it.

Change-Id: I7b51cb20f51b6dc571fcfa8dd53efe1dbd1e6985
diff --git a/tempest/services/volume/v1/json/admin/__init__.py b/tempest/services/volume/v1/json/admin/__init__.py
deleted file mode 100644
index e69de29..0000000
--- a/tempest/services/volume/v1/json/admin/__init__.py
+++ /dev/null
diff --git a/tempest/services/volume/v2/json/admin/__init__.py b/tempest/services/volume/v2/json/admin/__init__.py
deleted file mode 100644
index e69de29..0000000
--- a/tempest/services/volume/v2/json/admin/__init__.py
+++ /dev/null