Bump/test shibboleth to 2.5.4

[mrvisser]

Looks like 2.5.3 may have been removed from apt repositories. This error is occurring in the puppet run in staging on web0:

Error: Could not update: Execution of '/usr/bin/apt-get -q -y -o DPkg::Options::=--force-confold --force-yes install shibboleth=2.5.3-0switchaai1' returned 100: Reading package lists...
Building dependency tree...
Reading state information...
E: Version '2.5.3-0switchaai1' for 'shibboleth' was not found
Wrapped exception:
Execution of '/usr/bin/apt-get -q -y -o DPkg::Options::=--force-confold --force-yes install shibboleth=2.5.3-0switchaai1' returned 100: Reading package lists...
Building dependency tree...
Reading state information...
E: Version '2.5.3-0switchaai1' for 'shibboleth' was not found
Error: /Stage[main]/Shibboleth::Sp/Package[shibboleth]/ensure: change from 2.5.4-0switchaai1 to 2.5.3-0switchaai1 failed: Could not update: Execution of '/usr/bin/apt-get -q -y -o DPkg::Options::=--force-confold --force-yes install shibboleth=2.5.3-0switchaai1' returned 100: Reading package lists...
Building dependency tree...
Reading state information...
E: Version '2.5.3-0switchaai1' for 'shibboleth' was not found

We should upgrade and see if we can add it to our PPA to hold the version.

[mrvisser]

Assigned to @simong