evalmountdata: put back colon in .:mount syntax only if we removed it

evalmountdata: put back colon in .:mount syntax only if we removed it

we looked for a set character (not NULL) at cpos before, instead
of looking for a non-NULL pointer. fix it.

Reviewed-on: http://gerrit.openafs.org/3874
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: Derrick Brashear <shadow@dementia.org>
(cherry picked from commit d12d2c08eef5b2bffccefac61465b7d4e40bba9f)

Change-Id: I6920aa378361c1c78285b595303f32ed3194462b
Reviewed-on: http://gerrit.openafs.org/3875
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: Derrick Brashear <shadow@dementia.org>