Enable TestCallThatRestarts test on Linux.

This is related to:
http://llvm.org/bugs/show_bug.cgi?id=15278

I ran this 20 times in a row without failure at svn r202440 on Ubuntu
12.04 LTS x86_64 using July 2013 libedit and gcc 4.8.2.

llvm-svn: 202448

lldb/test/expression_command/call-restarts/TestCallThatRestarts.py

@@ -27,7 +27,6 @@ class ExprCommandWithTimeoutsTestCase(TestBase):
         self.call_function()
 
     @skipIfFreeBSD # llvm.org/pr15278
-    @skipIfLinux # llvm.org/pr15278: handle expressions that generate signals on Linux
     @dwarf_test
     def test_with_dwarf(self):
         """Test calling std::String member function."""