zdtm: Need add -Wno-unused-result option lib and static Makefile

It's need to add -Wno-unused-result option to lib and
static Makefile to avoid errors like:
msg.c:58:8: error: ignoring return value of 'write', declared with
attribute warn_unused_result [-Werror=unused-result]
Signed-off-by: Victor Konyashkin <vkonyashkin@parallels.com>
Acked-by: Andrey Vagin <avagin@parallels.com>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

test/zdtm/lib/Makefile

-CFLAGS	= -g -O2 -Wall -Werror
+CFLAGS	= -g -O2 -Wall -Werror -Wno-unused-result
 
 LIB	= libzdtmtst.a
 

test/zdtm/live/static/Makefile

 LIBDIR	= ../../lib
 LIB	= $(LIBDIR)/libzdtmtst.a
 override CPPFLAGS += -I$(LIBDIR)
-CFLAGS	= -g -O2 -Wall -Werror
+CFLAGS	= -g -O2 -Wall -Werror -Wno-unused-result
 
 TST_NOFILE	=				\
 		busyloop00			\