base: Replace last remaining sprintf'ed id.
base: Replace last remaining sprintf'ed id.

Loop unrolling is one of the most important graph optimizations, so it's
important this function is fast. This optimization is much faster than
the original code (about 50x faster on my development machine).

Change-Id: I51f8e1b8ff625918822d84abb5d5cf659fa35217

giosalv/526-aladdin,giosalv/526-aladdin,giosalv/526-aladdin,giosalv/526-aladdin