tools: ceph-detect-init: handle alt releases in CentOS

The release string can be something like "7 (AltArch)"

Signed-off-by: Nathan Cutler <ncutler@suse.com>

src/ceph-detect-init/ceph_detect_init/centos/__init__.py

@@ -3,11 +3,16 @@
 codename = None
 
 
+# handle release strings like "7 (AltArch)"
+def _rh_major_version(v):
+    return int("".join(itertools.takewhile(str.isdigit, v)))
+
+
 def choose_init():
     """Select a init system
 
     Returns the name of a init system (upstart, sysvinit ...).
     """
-    if release and int(release.split('.')[0]) >= 7:
+    if release and _rh_major_version(release) >= 7:
         return 'systemd'
     return 'sysvinit'