Revert "CID#705982 ensure umask for mkstemp"

This reverts commit 9ab99483808bad973363f1f27bb548c8628ace1d.  Coverity warning
about mkstemp without umask appears to be bogus (cf.
<https://communities.coverity.com/message/6516> "Why are uses of mkstemp
'without securely setting umask first' being flagged?) and calling umask is not
MT-safe, see fdo#60338 "FILESAVE: Saved files have incorrect permissions on
linux."
Revert "CID#705985 ensure umask for mkstemp"

This reverts commit 5f5a981dd6df406b7bbddd88fa0b701b5a8d2246.  Coverity warning
about mkstemp without umask appears to be bogus (cf.
<https://communities.coverity.com/message/6516> "Why are uses of mkstemp
'without securely setting umask first' being flagged?) and calling umask is not
MT-safe, see fdo#60338 "FILESAVE: Saved files have incorrect permissions on
linux."