support python 3 on centos 7

when installing with python 3.6 on centos7 pip installs
packages to /usr/local/bin as it does on new versions
of fedora.

this change updates the check to include centos

Change-Id: I7d16194d6ba1391ca31251d5b50cbb8de033fc38
diff --git a/inc/python b/inc/python
index ec7eb5b..419d5c5 100644
--- a/inc/python
+++ b/inc/python
@@ -49,7 +49,8 @@
     fi
     $xtrace
 
-    if python3_enabled && [[ "$os_VENDOR" == "Fedora" && $os_RELEASE -gt 26 ]]; then
+    if python3_enabled && [[ "$os_VENDOR" == "CentOS" ]] || \
+    [[ "$os_VENDOR" == "Fedora" && $os_RELEASE -gt 26 ]]; then
         # Default Python 3 install prefix changed to /usr/local in Fedora 27:
         # https://fedoraproject.org/wiki/Changes/Making_sudo_pip_safe
         echo "/usr/local/bin"