passpoint-r2: change the name for OSU_FAILURE_INVALID_SERVER_URL.

Currently OSU_FAILURE_INVALID_SERVER_URL name is confused with another
flag called (OSU_FAILURE_SERVER_URL_INVALID) that is used for connecting
OSU server.

So, it is better to change the name to meaningful name.

Bug: 119514793
Test: ./frameworks/base/wifi/tests/runtests.sh
Change-Id: I4dabe6bab12211faae7758b8fc2df2381efb6c21
Signed-off-by: Ecco Park <eccopark@google.com>