zdtm: fix awk script for Ubuntu

mawk doesn't handle '\<...\>'

Ubuntu:
$ awk -W version
mawk 1.3.3 Nov 1996, Copyright (C) Michael D. Brennan
$ ldd /bin/ps
	linux-vdso.so.1 =>  (0x00007fffb290a000)
$ ldd /bin/ps  | awk '/\<linux-vdso\.so\>/ { print $1 }'
$ ldd /bin/ps  | awk '/linux-vdso\.so/ { print $1 }'
linux-vdso.so.1

Fedora:
$ ldd /bin/ps
	linux-vdso.so.1 =>  (0x00007fff61fcb000)
$ ldd /bin/ps  | awk '/\<linux-vdso\.so\>/ { print $1 }'
linux-vdso.so.1
$ awk --version
GNU Awk 4.1.1, API: 1.1

Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>