push: respect --no-thin

push: respect --no-thin

- From the beginning of push.c in 755225d, 2006-04-29, "thin" option
  was enabled by default but could be turned off with --no-thin.

- Then Shawn changed the default to 0 in favor of saving server
  resources in a4503a1, 2007-09-09. --no-thin worked great.

- One day later, in 9b28851 Daniel extracted some code from push.c to
  create transport.c. He (probably accidentally) flipped the default
  value from 0 to 1 in transport_get().

From then on --no-thin is effectively no-op because git-push still
expects the default value to be false and only calls
transport_set_option() when "thin" variable in push.c is true (which
is unnecessary). Correct the code to respect --no-thin by calling
transport_set_option() in both cases.

receive-pack learns about --reject-thin-pack-for-testing option,
which only is for testing purposes, hence no document update.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>