clone: set submodule.recurse=true if submodule.stickyRecursiveClone enabled

clone: set submodule.recurse=true if submodule.stickyRecursiveClone enabled

Based on current experience, when running git clone --recurse-submodules,
developers do not expect other commands such as pull or checkout to run
recursively into active submodules. However, setting submodule.recurse=true
at this step could make for a simpler workflow by eliminating the need for
the --recurse-submodules option in subsequent commands. To collect more
data on developers' preference in regards to making submodule.recurse=true
a default config value in the future, deploy this feature under the opt in
submodule.stickyRecursiveClone flag.

Signed-off-by: Mahi Kolla <mkolla2@illinois.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>