Avoid pagination in attach.exp

Avoid pagination in attach.exp

While re-testing the complaint series, I saw some unresolved tests in
attach.exp.  In particular, the tests were failing because the pager
was active.

This is partly a new problem, introduced because that series changes
some prints from unfiltered to filtered.  However, it is also a latent
bug, which you can see by shrinking your window very small and then
running the test.

This patch avoids the problem by passing -quiet to gdb and arranging
to set the window height and width in one other test.

Arguably instead of -quiet we should disable the pager during gdb's
welcome message.  I can do that if it seems desirable; but meanwhile
this patch is safe.

gdb/testsuite/ChangeLog
2018-10-04  Tom Tromey  <tom@tromey.com>

	* gdb.base/attach.exp (test_command_line_attach_run): Use -quiet;
	set width and height to 0.
	(test_command_line_attach_run): Use -quiet.