Rate-limit while loop in SystemdService.is_active().

Previously is_active() was frenetically calling systemctl is_active in
tight loop which in fact made the process slower.

Reviewed-By: Martin Basti <mbasti@redhat.com>

ipaplatform/base/services.py

@@ -25,6 +25,7 @@ interacting with system services.
 
 import os
 import json
+import time
 
 import ipalib
 from ipapython import ipautil
@@ -53,6 +54,8 @@ wellknownports = {
     'pki-tomcatd': [8080, 8443],  # used if the incoming instance name is blank
 }
 
+SERVICE_POLL_INTERVAL = 0.1 # seconds
+
 
 class KnownServices(MagicDict):
     """
@@ -303,11 +306,13 @@ class SystemdService(PlatformService):
                 )
             except ipautil.CalledProcessError as e:
                 if e.returncode == 3 and 'activating' in str(e.output):
+                    time.sleep(SERVICE_POLL_INTERVAL)
                     continue
                 return False
             else:
                 # activating
                 if rcode == 3 and 'activating' in str(sout):
+                    time.sleep(SERVICE_POLL_INTERVAL)
                     continue
                 # active
                 if rcode == 0: