Disable the tests, cuts build time by half and avoids build issues
with extra dependencies.

Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>

diff -Nura libmemcached-1.0.18.orig/Makefile.am libmemcached-1.0.18/Makefile.am
--- libmemcached-1.0.18.orig/Makefile.am	2014-07-19 08:43:15.127031040 -0300
+++ libmemcached-1.0.18/Makefile.am	2014-07-19 08:48:11.327068987 -0300
@@ -76,7 +76,6 @@
 include libmemcachedinternal/util/include.am
 include rpm/include.mk
 include support/include.am
-include tests/include.am
 include util/include.am
 include win32/include.am