[gdb/testsuite] Fix command result testing in mi-complete.exp

When running gdb.mi/mi-complete.exp in conjunction with:
...
$ stress -c $(($(cat /proc/cpuinfo | grep -c "^processor") + 1))
...
we get less than 50% full passes:
...
$ for n in  $(seq 1 100); do \
    make V=1 -O check \
      'RUNTESTFLAGS=gdb.mi/mi-complete.exp --target_board=unix'; \
  done 2>&1 \
  | grep "expected passes" | sort | uniq -c
     45 # of expected passes            7
      9 # of expected passes            8
     46 # of expected passes            9
...

A diff between a passing and failing gdb.log shows this difference:
...
-&"set max-completions 1\n"
 2-complete br
+&"set max-completions 1\n"
...

The problem is that the test-case issues the "set max-completion <n>" command,
and without waiting for the output issues a next command, and tries to parse
the results of both commands, expecting a specific interleaving of the various
output streams.

Fix the FAIL by waiting for the result of the "set max-completion <n>" command
before issuing another command.

Tested on x86_64-linux.

gdb/testsuite/ChangeLog:

2019-07-23  Tom de Vries  <tdevries@suse.de>

	PR testsuite/24711
	* gdb.mi/mi-complete.exp: Wait for "set max-completions" result before
	issuing next command.

2 files changed, 10 insertions, 2 deletions

diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
index c575405..2f9c79a 100644
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -1,3 +1,9 @@
+2019-07-23  Tom de Vries  <tdevries@suse.de>
+
+	PR testsuite/24711
+	* gdb.mi/mi-complete.exp: Wait for "set max-completions" result before
+	issuing next command.
+
 2019-07-22  Andrew Burgess  <andrew.burgess@embecosm.com>
 
 	* gdb.ada/info_auto_lang.exp: Update expected results.
diff --git a/gdb/testsuite/gdb.mi/mi-complete.exp b/gdb/testsuite/gdb.mi/mi-complete.exp
index 692b004..5b96135 100644
--- a/gdb/testsuite/gdb.mi/mi-complete.exp
+++ b/gdb/testsuite/gdb.mi/mi-complete.exp
@@ -58,14 +58,16 @@ mi_gdb_test "-info-gdb-mi-command complete" \
 
 # Limit max completions and check that max_completions_reached=\"0\" is set
 # to 1.
-send_gdb "set max-completions 1\n"
+mi_gdb_test "set max-completions 1" ".*=cmd-param-changed.*\\^done" \
+    "set max-completions 1"
 
 mi_gdb_test "2-complete br" \
             ".*2\\^done,completion=\"br\[A-Za-z0-9-\]+\",matches=\\\[\"br\[A-Za-z0-9-\]+\"\\\],max_completions_reached=\"1\"" \
             "-complete br, max-completions 1"
 
 # Disable completions and check an error is returned
-send_gdb "set max-completions 0\n"
+mi_gdb_test "set max-completions 0" ".*=cmd-param-changed.*\\^done" \
+    "set max-completions 0"
 
 mi_gdb_test "3-complete br" \
             ".*3\\^error,msg=\".*" \