virtinst: ignore comments in keymap conf files

On a host system with keyboard configured to en-US, it was noticed
that virt-install created install XML with keymap='de'. The host
system did not have /etc/vconsole.conf, so /etc/sysconfig/keyboard
was the next file to check, which contained the following

KEYTABLE=""

Currently the parsing code does not ignore comments and incorrectly
parsed a 'de' keymap. Fix by ignoring any lines that start with '#'
after trimming whitespace.

tests/hostkeymap.py

@@ -32,5 +32,5 @@ class TestHostkeymap(unittest.TestCase):
 
         self.assertEquals(
                 hostkeymap._sysconfig_keyboard(_open("sysconfig-comments.txt")),
-                "de-latin1-nodeadkeys")
+                "")
 

virtinst/hostkeymap.py

@@ -71,6 +71,9 @@ def _sysconfig_keyboard(f):
         s = f.readline()
         if s == "":
             break
+        s = s.strip()
+        if s.startswith("#"):
+            continue
         if (re.search("KEYMAP", s) is not None or
             re.search("KEYTABLE", s) is not None or
            (re.search("KEYBOARD", s) is not None and