Merge ~powersj/cloud-init:1674317_fix_is_file into cloud-init:master

[Joshua Powers]

net: Fix incorrect call to isfile

Previous commit 5beecdf introduced a regression by calling
os.path.is_file, a non-existent function. This changes that call to use
os.path.isfile.

LP: #1674317

[Server Team CI bot (server-team-bot)]

PASSED: Continuous integration, rev:c82124dc89906cb833cbdaca43254238502e9155
https://jenkins.ubuntu.com/server/job/cloud-init-ci/143/
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diff --git a/cloudinit/net/eni.py b/cloudinit/net/eni.py
index 9d39a2b..f471e05 100644
--- a/cloudinit/net/eni.py
+++ b/cloudinit/net/eni.py
@@ -508,7 +508,7 @@ def available(target=None):
         if not util.which(p, search=search, target=target):
             return False
     eni = util.target_path(target, 'etc/network/interfaces')
-    if not os.path.is_file(eni):
+    if not os.path.isfile(eni):
         return False
 
     return True