Remove install-exec-local rule

Remove install-exec-local rule

Hi Daniel and all,

I am trying to run LXC on the CentOS 5.3 and the Linux kernel 2.6.30.
I found a problem with running the rpmbuild command.  The error message
is shown below:

$ rpmbuild -bb lxc.spec
	<snip>
 /usr/bin/install -c 'lxc-setcap' '/var/tmp/lxc-0.6.2-build/usr/bin/lxc-setcap'
 /usr/bin/install -c 'lxc-version' '/var/tmp/lxc-0.6.2-build/usr/bin/lxc-version'
mkdir: cannot create directory `/var/lib/lxc': Permission denied
make[3]: *** [install-exec-local] Error 1
make[3]: Leaving directory `/home/ryousei/rpm/BUILD/lxc-0.6.2/src/lxc'
make[2]: *** [install-am] Error 2
make[2]: Leaving directory `/home/ryousei/rpm/BUILD/lxc-0.6.2/src/lxc'
make[1]: *** [install-recursive] Error 1
make[1]: Leaving directory `/home/ryousei/rpm/BUILD/lxc-0.6.2/src'
make: *** [install-recursive] Error 1
error: Bad exit status from /var/tmp/rpm-tmp.26914 (%install)

RPM build errors:
    Bad exit status from /var/tmp/rpm-tmp.26914 (%install)

This patch removes 'install-exec-local' rule in Makefile.  It is not necessary,
and it causes rpmbuild failure on the CentOS 5.3.

Signed-off-by: Ryousei Takano <takano-ryousei@aist.go.jp>
Signed-off-by: Daniel Lezcano <dlezcano@fr.ibm.com>