added path validation for ssh config (eterbug #12807)

Status Job ID Name Coverage
  Build
passed #1718
rx-build
build and public

06:25

 
  Test
failed #1720
rx-tests
testsuite

05:11

 
Name Stage Failure
failed
testsuite Test There is an unknown failure, please try again
(==) Using system config directory "/usr/share/X11/xorg.conf.d"
pci id for fd 13: 80ee:beef, driver (null)
EGL_MESA_drm_image required.
xinit: connection to X server lost

waiting for X server to shut down (II) Server terminated successfully (0). Closing log file.

/home/gitlab-runner/builds/22a11031/0/rx-etersoft/nxssh/rx-testsuite
ERROR: Build failed: exit status 1