Delay import of DrmaaSessionFactory after runner initialization

Fix issue galaxyproject#2463, i.e. the regression introduced in galaxyproject#2102 by which Galaxy
no longer respects <param id="drmaa_library_path"> in config/job_conf.xml ,
preventing the use of multiple drmaa runners.

lib/galaxy/jobs/runners/drmaa.py

@@ -15,7 +15,6 @@
 from galaxy.jobs.handler import DEFAULT_JOB_PUT_FAILURE_MESSAGE
 from galaxy.jobs.runners import AsynchronousJobState, AsynchronousJobRunner
 from galaxy.util import asbool
-from pulsar.managers.util.drmaa import DrmaaSessionFactory
 
 drmaa = None
 
@@ -62,6 +61,7 @@ def __init__( self, app, nworkers, **kwargs ):
                                 'feature, please install it or correct the '
                                 'following error:\n%s: %s' %
                                 (exc.__class__.__name__, str(exc)))
+        from pulsar.managers.util.drmaa import DrmaaSessionFactory
 
         # Subclasses may need access to state constants
         self.drmaa_job_states = drmaa.JobState