tests: parse inode in /proc/pid/maps/correctly in run-backtrace-data.sh

tests: parse inode in /proc/pid/maps/correctly in run-backtrace-data.sh

The backtrace-data.c parsed the inode in /proc/pid/maps with
format "%*x".
This caused failure if inode is big. For example,
  7f269223d000-7f269226b000 r-xp 00000000 00:50 10224326387095067468       /home/...

The error likes below:
  -bash-4.4$ cat run-backtrace-data.sh.log
  backtrace-data: /home/engshare/elfutils/0.174/src/elfutils-0.174/tests/backtrace-data.c:110:
    maps_lookup: Assertion `errno == 0' failed.
  /home/engshare/elfutils/0.174/src/elfutils-0.174/tests/test-subr.sh: line 84:
    3123578 Aborted                 (core dumped)
    LD_LIBRARY_PATH="${built_library_path}${LD_LIBRARY_PATH:+:}$LD_LIBRARY_PATH" $VALGRIND_CMD "$@"
  data: no main
  -bash-4.4$
The reason is errno is ERANGE.

Fix the test with inode format string "%*u" as inode here is presented
as decimal numbers.

Suggested-by: Mark Wielaard <mark@klomp.org>
Signed-off-by: Yonghong Song <yhs@fb.com>