Search subdirectory for goldfish extra images

Acloud needs emu-extra-linux-system-images package to mix goldfish
images. The images are in a subdirectory in the package. Acloud
searches both the root and the subdirectory so that it is convenient
for the developers to create instances from downloaded artifacts.

Bug: 182523970
Test: acloud-dev create --avd-type goldfish -vv --local-instance \
      --local-image ./emu-extra-linux-system-images \
      --local-system-image ./aosp_x86-img \
      --local-tool ./otatools \
      --local-tool ./sdk-repo-linux-emulator
Change-Id: I90e9601f2394b82e1be5910e99390fb76850ad88
1 file changed