Fix gdb.base/solib-corrupted.exp after dtrace probes changes

Fix gdb.base/solib-corrupted.exp after dtrace probes changes

Commit 6f9b8491 (Adapt `info probes' to support printing probes of
different types.) added a new type column to "info probes".  That
caused a solib-corrupted.exp regression:

 ~~~~~~~~~~~~~~~~~~~~~
 Running /home/pedro/gdb/mygit/src/gdb/testsuite/gdb.base/solib-corrupted.exp ...
 FAIL: gdb.base/solib-corrupted.exp: corrupted list

		 === gdb Summary ===

 # of expected passes            2
 # of unexpected failures        1
 ~~~~~~~~~~~~~~~~~~~~~

Tested on x86_64 Fedora 20.

gdb/testsuite/ChangeLog:
2015-02-20  Pedro Alves  <palves@redhat.com>

	* gdb.base/solib-corrupted.exp: Expect "stap" as first column of
	info probes.