libfabric: don't install the osd.h headers

When configured --with-devel-headers, there's now 2 "osd.h" header
files in libfabric (in different dirs).  Automake's "install" target
didn't like this, and errored out.

Since embedding libfabric is a temporary measure, just avoid the
problem by not installing any libfabric headers.

opal/mca/common/libfabric/Makefile.am

@@ -218,13 +218,6 @@ lib@OPAL_LIB_PREFIX@mca_common_libfabric_noinst_la_SOURCES = $(headers) $(source
 lib@OPAL_LIB_PREFIX@mca_common_libfabric_noinst_la_CPPFLAGS = $(cppflags)
 lib@OPAL_LIB_PREFIX@mca_common_libfabric_noinst_la_LIBADD = $(libadd)
 
-# Conditionally install the header files
-
-if WANT_INSTALL_HEADERS
-opaldir = $(opalincludedir)/$(subdir)
-opal_HEADERS = $(headers)
-endif
-
 # These two rules will sym link the "noinst" libtool library filename
 # to the installable libtool library filename in the case where we are
 # compiling this component statically (case 2), described above).