RQF1770481 - Add IGTF CA signing key

Source of key is:

• https://wiki.egi.eu/wiki/EGI_IGTF_Release
• http://repository.egi.eu/sw/production/cas/1/GPG-KEY-EUGridPMA-RPM-3

Repository is already configured

gpg GPG-KEY-EUGridPMA-RPM-3
gpg: WARNING: no command supplied.  Trying to guess what you mean ...
pub   dsa1024 2005-07-12 [SCA]
      D12E922822BE64D50146188BC32D99C83CDBBC71
      uid           EUGridPMA Distribution Signing Key 3
      <info@eugridpma.org>

[UMD-4-EGI-trustanchors]
name=EGI-trustanchors
baseurl=http://repository.egi.eu/sw/production/cas/1/current
enabled=1
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/GPG-KEY-EUGridPMA-RPM-3