Clean up -ssh-key- tmp files.
Clean up -ssh-key- tmp files.

Some USER-ssh-key-ABC123 files are left behind in /tmp. Clean them
up. Change the array combining function from '+' to array_merge(). The
'+' operator throws away elements with matching keys, so additional
slice users were having a small number of tmp key files
lost. array_merge() preserves all numerically keyed elements in the
merge by appending to the resulting array.

charliemeyer/geni-portal,tcmitchell/geni-portal,charliemeyer/geni-portal,charliemeyer/geni-portal,tcmitchell/geni-portal,charliemeyer/geni-portal,tcmitchell/geni-portal,tcmitchell/geni-portal,tcmitchell/geni-portal,charliemeyer/geni-portal