set print symbol off in py-value.exp and scm-value.exp

set print symbol off in py-value.exp and scm-value.exp

I see the following fails on arm-none-eabi target,

print sn^M
$14 = 0x0 <_ftext>^M
(gdb) FAIL: gdb.python/py-value.exp: print sn

print sn^M
$14 = 0x0 <_ftext>^M
(gdb) FAIL: gdb.guile/scm-value.exp: print sn

as <_ftext> is unexpected.  This patch is to set print symbol off to
avoid printing this.

gdb/testsuite:

2014-08-24  Yao Qi  <yao@codesourcery.com>

	* gdb.guile/scm-value.exp (test_lazy_strings): Set print
	symbol off.
	* gdb.python/py-value.exp (test_lazy_strings): Likewise.