health 2.0: Move healthd_common.cpp

... so that the next CL has less diff.

Test: see next CL.
Change-Id: I5be187ab859a0b26d615b5ba7af9a26a07880181
diff --git a/health/2.0/default/healthd_common.cpp b/health/utils/libhealthloop/HealthLoop.cpp
similarity index 100%
rename from health/2.0/default/healthd_common.cpp
rename to health/utils/libhealthloop/HealthLoop.cpp