Fixes SIGALRM usage on Windows.

Issues:
Fixes #1349

Problem:
SIGALRM is not available on Windows

Analysis:
This makes the code fallback to not using the SIGALRM if it is not importable.

Tests:

Author: caphrim007

f5/bigip/__init__.py

@@ -25,6 +25,7 @@
 
 try:
     import signal
+    from signal import SIGALRM
     HAS_SIGNAL = True
 except ImportError:
     HAS_SIGNAL = False
@@ -114,7 +115,7 @@ def _get_tmos_version(self):
         connect = self._meta_data['bigip']._meta_data['icr_session']
         base_uri = self._meta_data['uri'] + 'tm/sys/'
         if HAS_SIGNAL:
-            signal.signal(signal.SIGALRM, timeout_handler)
+            signal.signal(SIGALRM, timeout_handler)
             signal.alarm(int(self.args['timeout']))
             response = connect.get(base_uri)
             signal.alarm(0)