qemu-iotests: make check-block.sh work on out-of-tree builds

Since check-block.sh, the "check" script has learnt to find the source
path.  On the other hand, it expects common.env to be in the build tree
(both changes made in commit 76c7560a, "configure: Enable out-of-tree
iotests", 2014-05-24).  So, it is wrong to invoke "check" from the source
path like check-block.sh does.  Fix it.
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
Message-id: 1450867341-11100-1-git-send-email-pbonzini@redhat.com
Signed-off-by: NMax Reitz <mreitz@redhat.com>

tests/check-block.sh

@@ -9,7 +9,7 @@ if [ ! -x $QEMU_PROG ]; then
     exit 1
 fi
 
-cd $SRC_PATH/tests/qemu-iotests
+cd tests/qemu-iotests
 
 ret=0
 ./check -T -nocache -raw || ret=1