tests: run all snap-confine tests in c-unit-tests task

[zyga]

This fixes older snap-confine tests. They got to bit-rot a little and required some changes:

• snap-confine relies on having SNAP_NAME set.
• to run /bin/true on i386 you need 32bit variants of some syscalls

Signed-off-by: Zygmunt Krynicki zygmunt.krynicki@canonical.com

[mvo5]

Yay!

[jdstrand]

Thanks for working on this! LGTM

[zyga]

FYI: while debugging 14.04 test failure issues we realized that there are two separate things that were broken. Our PPA contained an old version of libseccomp that unfortunately sorted as newer due to version mangling in the PPA. In addition the nocheck tests in debian/rules were incorrect or missing which prevented the package from building. The first issue was fixed directly by removing the offending package. The second issue is being addressed here #2567 and needs to be merged into the 14.04 release branch once it lands in master.