Static JAVA_XMX and JAVA_XX_MAXPERMSIZE env variables

[joshuabaird]

JAVA_XMX and JAVA_XX_MAXPERMSIZE have static values in templates/setenv.sh.header. You can override these by using "SETENV" on tomcat::instance, but the result is a confusing file where you have these variables defined twice that looks like this:

export DSUN_JAVA2D_OPENGL="false"
export DJAVA_AWT_HEADLESS="true"
export JAVA_XMX="256m"
export JAVA_XX_MAXPERMSIZE="256m"

export JAVA_XMX="28000m"
export JAVA_XX_MAXPERMSIZE="750m"

. $CATALINA_BASE/bin/setenv-local.sh

export JAVA_OPTS="-Dsun.java2d.opengl=${DSUN_JAVA2D_OPENGL} \
                  -Djava.awt.headless=${DJAVA_AWT_HEADLESS} \
                  -Xmx${JAVA_XMX} \
                  -XX:MaxPermSize=${JAVA_XX_MAXPERMSIZE} \
                  ${ADD_JAVA_OPTS}"

Is there a reason these are statically defined?