Ensure java executable is on the path.

Patch by Angelo Polo; reviewed by Aleksei Zotov, brandonwilliams and
edimitrova for CASSANDRA-14325

CHANGES.txt

@@ -1,4 +1,5 @@
 3.0.25:
+ * Ensure java executable is on the path (CASSANDRA-14325)
  * Make speculative retry parameter case-insensitive for backward compatibility with 2.1 (CASSANDRA-16467)
  * Push digest mismatch exceptions to trace (CASSANDRA-14900)
  * Support long names in nodetool output (CASSANDRA-14162)

bin/cassandra

@@ -98,7 +98,7 @@ if [ -n "$JAVA_HOME" ]; then
         fi
     done
 else
-    JAVA=java
+    JAVA=`command -v java 2> /dev/null`
 fi
 
 if [ -z $JAVA ] ; then

bin/debug-cql

@@ -36,7 +36,7 @@ fi
 if [ -n "$JAVA_HOME" ]; then
     JAVA="$JAVA_HOME/bin/java"
 else
-    JAVA=java
+    JAVA=`command -v java 2> /dev/null`
 fi
 
 if [ -z "$CASSANDRA_CONF" -o -z "$CLASSPATH" ]; then