fix expansion of LXCPATH,LXCROOTFSMOUNT,LXCTEMPLATEDIR

fix expansion of LXCPATH,LXCROOTFSMOUNT,LXCTEMPLATEDIR

These variables are not expanded correctly in doc/lxc-create.sgml.in
and a workaround is in place to ensure ${localstatedir}, and ${datadir}
are set in the various shell scripts that use it. There is no workaround
to ensure ${datadir} is set in src/lxc/lxc-create.in, nor is
${localstatedir} set in templates/lxc-altlinux.in so I think that these
are currently broken.

Using AS_AC_EXPAND instead of AC_SUBST fixes these problems and removes
the need for the workarounds. In addition the lxc-start-ephemeral.in
script can be autoconf'ed instead of sed'ed by the makefile.

Signed-off-by: Dwight Engen <dwight.engen@oracle.com>