[3079] Disable the memory manager if no shared memory

Just ifdef out the whole makefiles.

src/bin/memmgr/Makefile.am

+if USE_SHARED_MEMORY
+
+# If we don't have shared memory, the memory manager is useless.
+# Skip building, testing and installing it completely.
+
 SUBDIRS = . tests
 
 pkglibexecdir = $(libexecdir)/@PACKAGE@
@@ -60,3 +65,5 @@ install-data-hook:
 
 clean-local:
 	rm -rf $(CLEANDIRS)
+
+endif

src/lib/python/isc/memmgr/Makefile.am

+if USE_SHARED_MEMORY
+
+# We use the memory manager only with shared memory. No reason to
+# install on platforms without it and tests may fail there.
+
 SUBDIRS = . tests
 
 python_PYTHON = __init__.py builder.py datasrc_info.py logger.py
@@ -23,3 +28,5 @@ CLEANDIRS = __pycache__
 
 clean-local:
 	rm -rf $(CLEANDIRS)
+
+endif