Add suffix .so to use directly libart.so

It should be the complete name with suffix .so to use libart.
At present, unnecessarily falls back like below.
"Falling back from libart to libart.so after dlopen error:
dlopen failed: library "libart" not found"

Change-Id: Ie5da35a71d6661434d2097c842407e6a254f8f58
Signed-off-by: randy.jeong <randy.jeong@samsung.com>