PhysicalConsole: rename _exec() to _pexpect_spawn()
PhysicalConsole: rename _exec() to _pexpect_spawn()

Signed-off-by: Zack Cerza <d7cdf09fc0f0426e98c9978ee42da5d61fa54986@redhat.com>

SUSE/teuthology,SUSE/teuthology,ceph/teuthology,ktdreyer/teuthology,dmick/teuthology,dmick/teuthology,ceph/teuthology,ktdreyer/teuthology,dmick/teuthology,SUSE/teuthology