$HOME might not be available in build chroots, use /tmp instead

--- a/expected/start_memcached.out
+++ b/expected/start_memcached.out
@@ -1 +1 @@
-\! memcached -p 33211 -P $HOME/.pgmemcache-memcached.pid -d
+\! memcached -p 33211 -P /tmp/pgmemcache-memcached.pid -d
--- a/expected/stop_memcached.out
+++ b/expected/stop_memcached.out
@@ -1 +1 @@
-\! kill `cat $HOME/.pgmemcache-memcached.pid`
+\! kill `cat /tmp/pgmemcache-memcached.pid`
--- a/sql/start_memcached.sql
+++ b/sql/start_memcached.sql
@@ -1 +1 @@
-\! memcached -p 33211 -P $HOME/.pgmemcache-memcached.pid -d
+\! memcached -p 33211 -P /tmp/pgmemcache-memcached.pid -d
--- a/sql/stop_memcached.sql
+++ b/sql/stop_memcached.sql
@@ -1 +1 @@
-\! kill `cat $HOME/.pgmemcache-memcached.pid`
+\! kill `cat /tmp/pgmemcache-memcached.pid`
