Disable compression in AdbPull()

Compression makes adb pull slower, enough to make the /vendor pull
in vts_vndk_dependency_test time out on some devices.

Commit I9ed6f37bc55b1d55ae7c0c29a70a0e79b91ff683 updates the default
for adb pull, but VTS may run with an older version. Setting the
ADB_COMPRESSION environment variable to 0 will disable compression
for all versions supporting it, and does no harm otherwise.

This change takes vts_vndk_dependency_test from 396 to 181 seconds
on my device, allowing it to finish within the 6-minute deadline.

Change-Id: Ic0a5e5e5ac07a78f593619487c66376ab1a417df
1 file changed