install memcached for swift via files

when swift was enabled we were installing memcached via
stack.sh, after marking it optional in files. Just use
files instead.

Change-Id: Ib8ee2d1f47254e805f4747b8aff6e89baa66913c
diff --git a/files/apts/swift b/files/apts/swift
index f298377..c52c68b 100644
--- a/files/apts/swift
+++ b/files/apts/swift
@@ -1,6 +1,6 @@
 curl
 gcc
-memcached # NOPRIME
+memcached
 python-configobj
 python-coverage
 python-dev
diff --git a/files/rpms/swift b/files/rpms/swift
index c9d49e9..ce41ceb 100644
--- a/files/rpms/swift
+++ b/files/rpms/swift
@@ -1,6 +1,6 @@
 curl
 gcc
-memcached # NOPRIME
+memcached
 python-configobj
 python-coverage
 python-devel
diff --git a/stack.sh b/stack.sh
index 084f276..8947382 100755
--- a/stack.sh
+++ b/stack.sh
@@ -784,11 +784,6 @@
     fi
 fi
 
-if is_service_enabled swift; then
-    # Install memcached for swift.
-    install_package memcached
-fi
-
 TRACK_DEPENDS=${TRACK_DEPENDS:-False}
 
 # Install python packages into a virtualenv so that we can track them