Fix package path of android/soong/android pctx

android/soong/common was renamed to android/soong/android long
ago, but the pctx package path was still "android/soong/common".
This required all users of rules defined in android/soong/android
to import "android/soong/android" and then
pctx.Import("android/soong/common").

Test: m checkbuild
Change-Id: I20d096522760538f7cfc2bec3d4bfeba99b275d4