test: Run LUKS tests with more VM memory
test: Run LUKS tests with more VM memory

In recent versions, cryptsetup uses memory-hard PBKDF, which overflows
our default 1 GiB of RAM. Run the tests with 1.5 GiB to avoid that,
which is the minimum requirement for CentOS 8 [1]. See [2] for details.

[1] https://wiki.centos.org/About/Product
[2] https://bugzilla.redhat.com/show_bug.cgi?id=1881829

Closes #14658
garrett/cockpit,cockpit-project/cockpit,deryni/cockpit,moraleslazaro/cockpit,garrett/cockpit,martinpitt/cockpit,moraleslazaro/cockpit,garrett/cockpit,moraleslazaro/cockpit,moraleslazaro/cockpit,deryni/cockpit,cockpit-project/cockpit,mvollmer/cockpit,cockpit-project/cockpit,cockpit-project/cockpit,martinpitt/cockpit,deryni/cockpit,mvollmer/cockpit,martinpitt/cockpit,garrett/cockpit,deryni/cockpit,garrett/cockpit,cockpit-project/cockpit,mvollmer/cockpit,moraleslazaro/cockpit,deryni/cockpit,martinpitt/cockpit,martinpitt/cockpit,mvollmer/cockpit,mvollmer/cockpit,moraleslazaro/cockpit,deryni/cockpit,moraleslazaro/cockpit,deryni/cockpit