SDK Repository: switch to sdk addon revision 6.

addon-6.xsd changes <extra><revision> from an int (major only)
to a full <revision> element with major.micro.minor (but not
preview part.)

(cherry picked from commit 7657a590830cfe87fb2dc6ff03c0dcb7589c0bdf)

Change-Id: Iedff23a757dd3fd8d9e8006a2aec072ce2c71e8d
1 file changed