tests: Fix broken targets check-report-qtest-*

They need QTEST_QEMU_IMG. Without it, the tests raise an assertion:

$ make -C bin check-report-qtest-i386.xml
make: Entering directory 'bin'
GTESTER check-report-qtest-i386.xml
blkdebug: Suspended request 'A'
blkdebug: Resuming request 'A'
ahci-test: tests/libqos/libqos.c:162:
 mkimg: Assertion `qemu_img_path' failed.
main-loop: WARNING: I/O thread spun for 1000 iterations
Signed-off-by: NStefan Weil <sw@weilnetz.de>
Reviewed-by: NJohn Snow <jsnow@redhat.com>
Message-id: 1437231284-17455-1-git-send-email-sw@weilnetz.de
Signed-off-by: NJohn Snow <jsnow@redhat.com>

tests/Makefile

@@ -478,6 +478,7 @@ $(patsubst %, check-%, $(check-unit-y)): check-%: %
 
 $(patsubst %, check-report-qtest-%.xml, $(QTEST_TARGETS)): check-report-qtest-%.xml: $(check-qtest-y)
 	$(call quiet-command,QTEST_QEMU_BINARY=$*-softmmu/qemu-system-$* \
+		QTEST_QEMU_IMG=qemu-img$(EXESUF) \
 	  gtester -q $(GTESTER_OPTIONS) -o $@ -m=$(SPEED) $(check-qtest-$*-y),"GTESTER $@")
 
 check-report-unit.xml: $(check-unit-y)