Add support for OL7 and older other EL7 flavors

Older EL7 didn't have platform-python in installer,
change to fallback to old /usr/bin/python if
needed.

confluent_osdeploy/el7/profiles/default/scripts/functions

@@ -60,7 +60,11 @@ run_remote_python() {
     mkdir -p $(dirname $1)
     curl -f -sS $curlargs https://$mgr/confluent-public/os/$profile/scripts/$1 > $1
     if [ $? != 0 ]; then echo "'$*'" failed to download; return 1; fi
-    /usr/libexec/platform-python $*
+    if [ -x /usr/libexec/platform-python ]; then
+        /usr/libexec/platform-python $*
+    else
+        /usr/bin/python $*
+    fi
     retcode=$?
     echo "'$*' exited with code $retcode"
     cd - > /dev/null

confluent_server/confluent/osimage.py

@@ -346,7 +346,7 @@ def _priv_check_oraclelinux(isoinfo):
     ver = None
     arch = None
     for entry in isoinfo[0]:
-        if 'oraclelinux-release-8' in entry:
+        if 'oraclelinux-release-' in entry:
             ver = entry.split('-')[2]
             arch = entry.split('.')[-2]
             break