Dexdiag returns error when no maps found

When dexdiag does not find a mapping that is either from an oat or from
a vdex, it returns a non-zero exit status.

Bug: 35800981
Test: make -j 40 test-art-target-gtest-dexdiag_test
Change-Id: I346dd2f578b89ce16305f4118a0749ac62ba8e1d