zdtm: exclude vdso before modifing output of ldd

ldd pipe00:
linux-vdso.so.1 =>  (0x00007fffbb0cb000)

Currently the first part of line is dropts, if the line contains "=>",
so we need to exclude vdso, before modifing lines.

This patch fixes bug:
$ zdtm.sh ns/static/pipe00
Failed at  (0x00007fffa49fe000)
Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

test/zdtm.sh

@@ -235,7 +235,7 @@ construct_root()
 	#	libc.so.6 => /lib/arm-linux-gnueabihf/libc.so.6 (0xb6dc5000)
 	#	/lib/ld-linux-armhf.so.3 (0xb6f0b000)
 
-	for i in `ldd $test_path $ps_path | grep -P '^\s' | sed "s/.*=> //" | awk '{ print $1 }' | grep -v vdso`; do
+	for i in `ldd $test_path $ps_path | grep -P '^\s' | grep -v vdso | sed "s/.*=> //" | awk '{ print $1 }'`; do
 		local lib=`basename $i`
 		[ -f $libdir/$lib ] && continue ||
 		[ -f $i ] && cp $i $libdir && cp $i $libdir2 && continue ||