[gdb/testsuite] Fix python.exp with check-read1

[gdb/testsuite] Fix python.exp with check-read1

when running python/python.exp with check-read1, we get:
...
(gdb) PASS: gdb.python/python.exp: prompt substitution readline - end
python gdb.prompt_hook = error_prompt^M
Python Exception <type 'exceptions.RuntimeError'> Python exception calledPASS: gdb.python/python.exp: set hook
: ^M
(gdb) PASS: gdb.python/python.exp: set the hook to default
python gdb.prompt_hook = None^M
(gdb) PASS: gdb.python/python.exp: set print-stack full for prompt error test
set python print-stack full^M
(gdb) FAIL: gdb.python/python.exp: set the hook
python gdb.prompt_hook = error_prompt^M
Traceback (most recent call last):^M
  File "<string>", line 3, in error_prompt^M
RuntimeError: Python exception called^M
(gdb) FAIL: gdb.python/python.exp: set the hook to default
...

The problem is that gdb_test_multiple here:
...
gdb_test_multiple "python gdb.prompt_hook = error_prompt" "set the hook" {
    -re "Python Exception (exceptions.RuntimeError|<(type 'exceptions.|class ')RuntimeError'>) Python excepti
on called.*" {
       pass "set hook"
    }
}
...
specifies a regexp that ends with ".*" but doesn't specify the expected
$gdb_prompt.

Consequently, due to check-read1, the ".*" is matched to "" and the remaining
$gdb_prompt  is read by the the following gdb_py_test_silent_cmd, which has
its own $gdb_prompt read by the following gdb_py_test_silent_cmd, which has
its own $gdb_prompt causing a mismatch for the following gdb_test_multiple:
...
gdb_test_multiple "python gdb.prompt_hook = error_prompt" "set the hook" {
    -re "Traceback.*File.*line.*RuntimeError.*Python exception called.*" {
        pass "set hook"
    }
}
...
which causes both FAILs.

The second gdb_test_multiple has the same problem as the first, but it happens
not to cause a FAIL because it's followed by a gdb_py_test_silent_cmd and a
clean_restart.

Fix the regexps in both gdb_test_multiple calls.

Tested on x86_64-linux.

gdb/testsuite/ChangeLog:

2019-07-29  Tom de Vries  <tdevries@suse.de>

	* gdb.python/python.exp: Don't terminate gdb_test_multiple regexp
	with ".*".