speedup get_build() of jenkinsapi python module

gistfile1.txt

diff --git a/jenkinsapi/job.py b/jenkinsapi/job.py
index 280cf93..20c6932 100644
--- a/jenkinsapi/job.py
+++ b/jenkinsapi/job.py
@@ -90,7 +90,7 @@ class Job(JenkinsBase, MutableJenkinsThing):

     def poll(self, tree=None):
         data = super(Job, self).poll(tree=tree)
-        if not tree:
+        if not tree and self.jenkins.lazy is False:
             self._data = self._add_missing_builds(self._data)
         else:
             return data
@@ -392,7 +392,7 @@ class Job(JenkinsBase, MutableJenkinsThing):
     def get_build(self, buildnumber):
         assert isinstance(buildnumber, int)
         try:
-            url = self.get_build_dict()[buildnumber]
+            url = self.url + str(buildnumber)
             return Build(url, buildnumber, job=self)
         except KeyError:
             raise NotFound('Build #%s not found' % buildnumber)