Fix unstable test names in gdb.threads/attach-into-signal.exp

Currently, if you diff testsuite/gdb.sum of two testsuite runs you'll
often see spurious hunks like these:

  -PASS: gdb.threads/attach-into-signal.exp: nonthreaded: attempt 2: attach (pass 2), pending signal catch
  +PASS: gdb.threads/attach-into-signal.exp: nonthreaded: attempt 1: attach (pass 2), pending signal catch
   PASS: gdb.threads/attach-into-signal.exp: successfully compiled posix threads test case
   PASS: gdb.threads/attach-into-signal.exp: threaded: handle SIGALRM stop print pass
  -PASS: gdb.threads/attach-into-signal.exp: threaded: attempt 1: attach (pass 1), pending signal catch
  -PASS: gdb.threads/attach-into-signal.exp: threaded: attempt 1: attach (pass 2), pending signal catch
  +PASS: gdb.threads/attach-into-signal.exp: threaded: attempt 2: attach (pass 1), pending signal catch
  +PASS: gdb.threads/attach-into-signal.exp: threaded: attempt 4: attach (pass 2), pending signal catch

Fix this by removing the "attempt $attempt" test prefix.  The attempt
number can be retrieved from gdb.log instead, since the testcase is
already using "verbose -log" to that effect.

(The 'with_test_prefix "stoppedtry $stoppedtry"' prefix is unnecessary
too, because inside that block there are no pass/fail calls.  In fact
the block includes a comment saying:

  # No PASS message as we may be looping in multiple
  # attempts.

but I'll drop that whole loop in the next patch instead.)

After this commit we'll show:

  PASS: gdb.threads/attach-into-signal.exp: nonthreaded: handle SIGALRM stop print pass
  PASS: gdb.threads/attach-into-signal.exp: nonthreaded: attach (pass 1), pending signal catch
  PASS: gdb.threads/attach-into-signal.exp: nonthreaded: attach (pass 2), pending signal catch
  PASS: gdb.threads/attach-into-signal.exp: successfully compiled posix threads test case
  PASS: gdb.threads/attach-into-signal.exp: threaded: handle SIGALRM stop print pass
  PASS: gdb.threads/attach-into-signal.exp: threaded: attach (pass 1), pending signal catch
  PASS: gdb.threads/attach-into-signal.exp: threaded: attach (pass 2), pending signal catch

(I've avoided reindenting to make the patch easier to maintain/read.
I'll reindent the blocks after this is in.)

gdb/testsuite/ChangeLog:
2017-10-24  Pedro Alves  <palves@redhat.com>

	* gdb.threads/attach-into-signal.exp (corefunc): Remove "attach
	$attempt" test prefix.

2 files changed, 5 insertions, 2 deletions

diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
index c0a1417..0038a0c 100644
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -1,5 +1,10 @@
 2017-10-24  Pedro Alves  <palves@redhat.com>
 
+	* gdb.threads/attach-into-signal.exp (corefunc): Remove "attach
+	$attempt" and "stoppedtry $stoppedtry" test prefixes.
+
+2017-10-24  Pedro Alves  <palves@redhat.com>
+
 	* lib/gdb-python.exp (get_python_valueof): Add 'test' optional
 	parameter and handle it.  Don't output read value in test name.
 
diff --git a/gdb/testsuite/gdb.threads/attach-into-signal.exp b/gdb/testsuite/gdb.threads/attach-into-signal.exp
index cfb06cf..7502479 100644
--- a/gdb/testsuite/gdb.threads/attach-into-signal.exp
+++ b/gdb/testsuite/gdb.threads/attach-into-signal.exp
@@ -56,7 +56,6 @@ proc corefunc { threadtype executable } {
 	set attempt 1
 	set passes 1
 	while { $passes < 3 && $attempt <= $attempts } {
-	    with_test_prefix "attempt $attempt" {
 		set stoppedtry 0
 		while { $stoppedtry < 10 } {
 		    with_test_prefix "stoppedtry $stoppedtry" {
@@ -128,7 +127,6 @@ proc corefunc { threadtype executable } {
 		}
 
 		gdb_test "detach" "Detaching from.*" ""
-	    }
 	}
 
 	if {$passes < 3} {