[gdb/testsuite] Fix gdb.base/break-interp.exp timeout with check-read1

[gdb/testsuite] Fix gdb.base/break-interp.exp timeout with check-read1

With gdb.base/break-interp.exp and check-read1, we run get:
...
FAIL: gdb.base/break-interp.exp: LDprelinkNOdebugNO: \
  BINprelinkNOdebugNOpieNO: symbol-less: info files (timeout)
FAIL: gdb.base/break-interp.exp: LDprelinkNOdebugNO: \
  BINprelinkNOdebugNOpieYES: symbol-less: info files (timeout)
FAIL: gdb.base/break-interp.exp: LDprelinkNOdebugIN: \
  BINprelinkNOdebugNOpieNO: symbol-less: info files (timeout)
FAIL: gdb.base/break-interp.exp: LDprelinkNOdebugIN: \
  BINprelinkNOdebugNOpieYES: symbol-less: info files (timeout)
...

Fix this by calling exp_continue after each "info files" line.

Tested on x86_64-linux.

gdb/testsuite/ChangeLog:

2019-08-01  Tom de Vries  <tdevries@suse.de>

	PR testsuite/24863
	* gdb.base/break-interp.exp: Use exp_continue after each "info files"
	line.