scripts: improve message when TAP based tests fail

If one of the qtests fails, the TAP driver prints out a message like:

  ERROR - too few tests run (expected 3, got 1)

which fails to tell you which test program failed. This is a critical
ommission when many tests are running in parallel as their output is
interleaved. The improved message is:

  ERROR endianness-test - too few tests run (expected 3, got 1)

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Message-Id: <20200706125054.2619012-1-berrange@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

scripts/tap-driver.pl

@@ -217,7 +217,7 @@ sub report ($;$)
 
 sub testsuite_error ($)
 {
-  report "ERROR", "- $_[0]";
+  report "ERROR", "$test_name - $_[0]";
 }
 
 sub handle_tap_result ($)