Extracted some logic to utils_default.cpp in order to make platform specific overriding easier

Test: manual - could install and remove an app. As this is
refactoring there is no need for automated tests.

Change-Id: Ia9321de6699c69fbb7cfa9cf43edde102d56d532
diff --git a/cmds/installd/utils.h b/cmds/installd/utils.h
index 430f515..5afe059 100644
--- a/cmds/installd/utils.h
+++ b/cmds/installd/utils.h
@@ -117,6 +117,8 @@
 
 int delete_dir_contents_fd(int dfd, const char *name);
 
+int rm_package_dir(const std::string& package_dir);
+
 int copy_dir_files(const char *srcname, const char *dstname, uid_t owner, gid_t group);
 
 int64_t data_disk_free(const std::string& data_path);