TS-4248: allow metrics to change type on upgrade
TS-4248: allow metrics to change type on upgrade

New software versions can alter the type of metrics, but when that
happens, the metric from the previous software version has already
been restored from persistence. In this case, we can allow the type
of the metric to change to match the new registration.

chitianhao/trafficserver,rpufky/trafficserver,PSUdaemon/trafficserver,bryancall/trafficserver,taoyunxing/trafficserver,persiaAziz/trafficserver,reveller/trafficserver,davidbz/trafficserver,rpufky/trafficserver,dyrock/trafficserver,davidbz/trafficserver,rpufky/trafficserver,vmamidi/trafficserver,duke8253/trafficserver,rahmalik/trafficserver,reveller/trafficserver,dyrock/trafficserver,PSUdaemon/trafficserver,rpufky/trafficserver,bryancall/trafficserver,pbchou/trafficserver,rahmalik/trafficserver,duke8253/trafficserver,clearswift/trafficserver,davidbz/trafficserver,taoyunxing/trafficserver,SolidWallOfCode/trafficserver,PSUdaemon/trafficserver,reveller/trafficserver,reveller/trafficserver,persiaAziz/trafficserver,clearswift/trafficserver,chenglongwei/trafficserver,pbchou/trafficserver,clearswift/trafficserver,chitianhao/trafficserver,vmamidi/trafficserver,chenglongwei/trafficserver,duke8253/trafficserver,PSUdaemon/trafficserver,taoyunxing/trafficserver,reveller/trafficserver,clearswift/trafficserver,reveller/trafficserver,bryancall/trafficserver,duke8253/trafficserver,persiaAziz/trafficserver,dyrock/trafficserver,SolidWallOfCode/trafficserver,clearswift/trafficserver,pbchou/trafficserver,dyrock/trafficserver,SolidWallOfCode/trafficserver,chenglongwei/trafficserver,chitianhao/trafficserver,duke8253/trafficserver,dyrock/trafficserver,rahmalik/trafficserver,pbchou/trafficserver,SolidWallOfCode/trafficserver,vmamidi/trafficserver,pbchou/trafficserver,PSUdaemon/trafficserver,SolidWallOfCode/trafficserver,clearswift/trafficserver,taoyunxing/trafficserver,davidbz/trafficserver,persiaAziz/trafficserver,SolidWallOfCode/trafficserver,chenglongwei/trafficserver,taoyunxing/trafficserver,rahmalik/trafficserver,chitianhao/trafficserver,duke8253/trafficserver,persiaAziz/trafficserver,PSUdaemon/trafficserver,rpufky/trafficserver,taoyunxing/trafficserver,persiaAziz/trafficserver,chenglongwei/trafficserver,davidbz/trafficserver,rpufky/trafficserver,rahmalik/trafficserver,persiaAziz/trafficserver,rpufky/trafficserver,persiaAziz/trafficserver,PSUdaemon/trafficserver,chenglongwei/trafficserver,chitianhao/trafficserver,rahmalik/trafficserver,dyrock/trafficserver,taoyunxing/trafficserver,rahmalik/trafficserver,taoyunxing/trafficserver,dyrock/trafficserver,clearswift/trafficserver,PSUdaemon/trafficserver,reveller/trafficserver,rpufky/trafficserver,clearswift/trafficserver,davidbz/trafficserver,chitianhao/trafficserver,reveller/trafficserver,rpufky/trafficserver,chenglongwei/trafficserver,vmamidi/trafficserver,taoyunxing/trafficserver,reveller/trafficserver,rahmalik/trafficserver,bryancall/trafficserver,chenglongwei/trafficserver,chitianhao/trafficserver,clearswift/trafficserver,vmamidi/trafficserver,pbchou/trafficserver,PSUdaemon/trafficserver,duke8253/trafficserver,bryancall/trafficserver,SolidWallOfCode/trafficserver,vmamidi/trafficserver,rahmalik/trafficserver,bryancall/trafficserver