gdb/testsuite/tui: Always dump_screen when asked

gdb/testsuite/tui: Always dump_screen when asked

The Term::dump_screen routine currently dumps the screen using calls
to 'verbose', this means it will only dump the screen when the
testsuite is running in verbose mode.

However, the Term::dump_screen is most often called when a test fails,
in this case I think it is useful to have the screen dumped even when
we're not in verbose mode.

This commit changes the calls to 'verbose' to be 'verbose -log' so we
always get the screen dump.

gdb/testsuite/ChangeLog:

	* lib/tuiterm.exp (Term::dump_screen): Always dump the screen when
	called.

Change-Id: I5f0a7f5ac2ece04d6fe6e9c5a28ea2a0dda38955