Fix fail in gdb.mi/mi-reverse.exp

Commit 38b022b4 adds "method" and
"format" fields in =record-started, but doesn't update test case
gdb.mi/mi-reverse.exp, so it causes the fail like this,

PASS: gdb.mi/mi-reverse.exp: mi runto main
Expecting: ^(-interpreter-exec console record[^M
]+)?(=record-started,thread-group="i1"^M
\^done[^M
]+[(]gdb[)] ^M
[ ]*)
-interpreter-exec console record^M
=record-started,thread-group="i1",method="full"^M
^done^M
(gdb) ^M
FAIL: gdb.mi/mi-reverse.exp: Turn on process record

and regression was found by buildbot too
https://sourceware.org/ml/gdb-testers/2016-q2/msg04492.html

gdb/testsuite:

2016-07-05  Yao Qi  <yao.qi@linaro.org>

	* gdb.mi/mi-reverse.exp: Match =record-started output.