agent: moved command execution code into a separate file

Signed-off-by: Olaf Kirch <okir@suse.de>
__ni_process_find_path: path searching was broken

Signed-off-by: Olaf Kirch <okir@suse.de>
prepare for process execution with pty support: refactor some code in process.c

Signed-off-by: Olaf Kirch <okir@suse.de>
more process refactoring: make process.stdin a buffer as well

Signed-off-by: Olaf Kirch <okir@suse.de>
When creating nested test cases with the same name, the server would flag an error

This was because we were checking recursively not just the context in which
the test was being created, but all parent contexts as well.

Signed-off-by: Olaf Kirch <okir@suse.de>
Add support for running commands inside a pty

Signed-off-by: Olaf Kirch <okir@suse.de>
ni_process_t: rename fdpair[] to master_fd/slave_fd

Signed-off-by: Olaf Kirch <okir@suse.de>