liblog: use unique log tags for is_loggable tests

Apparently these tests are run in parallel, which causes errors since
they use the same log tag.  Use unique log tags based on pid to fix

Also re-enable the previously disabled tests.

Bug: 162669552
Test: run these tests 100x+ and see that they no longer fail
Change-Id: Ib20d638e5e559bca23adec479a5dcf64075e376e
1 file changed