Fix parallel testing issues in gdb.guile tests

Fix parallel testing issues in gdb.guile tests

Some gdb.guile tests such as scm-error.exp copies .scm file to
${subdir}/, how ${subdir} doesn't exist in parallel testing
(outputs/${subdir} exists).

$ make -j3 check TESTS='gdb.guile/scm-section-script.exp gdb.guile/scm-error.exp gdb.guile/scm-frame-args.exp'

ERROR: remote_download to host of ../../../../git/gdb/testsuite/gdb.guile/scm-section-script.scm to gdb.guile/t-scm-section-script.scm: cp: cannot create regular file 'gdb.guile/t-scm-section-script.scm': No such file or directory
ERROR: remote_download to host of ../../../../git/gdb/testsuite/gdb.guile/scm-frame-args.scm to gdb.guile/t-scm-frame-args.scm: cp: cannot create regular file
'gdb.guile/t-scm-frame-args.scm': No such file or directory
ERROR: remote_download to host of ../../../../git/gdb/testsuite/gdb.guile/scm-error-1.scm to gdb.guile/t-scm-error-1.scm: cp: cannot create regular file 'gdb.guile/t-scm-error-1.scm': No such file or directory

This patch is to remove the third argument of gdb_remote_download, so
that gdb_remote_download can return the correct location.

Further, these tests only copy .scm files to a different name.  From what
I can tell from the comments, looks we do this to avoid clobbering file
in in-tree build.  However, if source and dest of copy are the same, the
operation is no-op.  So it makes few sense to copy .scm files to a
different names.  I tried in-tree build/test with this patch, test
result isn't changed.

gdb/testsuite:

2014-12-05  Yao Qi  <yao@codesourcery.com>

	* gdb.guile/scm-error.exp: Remove the third argument to
	gdb_remote_download.
	* gdb.guile/scm-frame-args.exp: Likewise.
	* gdb.guile/scm-section-script.exp: Likewise.