[3079] Fix typo in directory name

src/lib/python/isc/Makefile.am

@@ -1,5 +1,5 @@
 SUBDIRS = datasrc util cc config dns log net notify testutils acl bind10
-SUBDIRS += xfrin log_messages server_common ddns sysinfo statistic
+SUBDIRS += xfrin log_messages server_common ddns sysinfo statistics
 if USE_SHARED_MEMORY
 # The memory manager is useless without shared memory support
 SUBDIRS += memmgr