t5500: Modernize test style

t5500: Modernize test style

Code outside of the test harness was emitting "Initializing..." from
git-init. Fixup this test to be more modern:

    - test_expect_object_count() and count_objects() are unused

    - use grep directly instead of test "..." = $(grep ...)

    - end the test_expect_success line with a single-quote and put the
      test on a new line

    - put as much code inside the test harness as possible

    - no_strict_count_check is unused and duplicates the test
      "new object count"

    - use && whenever possible to catch errors early

    - use test_tick instead of GIT_AUTHOR_DATE=$sec

    - remove debugging aid log.txt

    - use subshells instead of cd-ing around

Also merge the pull test into one large test.

Signed-off-by: Stephen Boyd <bebarino@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>