Fix some checks in lvm-utils.sh. Note that "$(test ...)" is always empty, since

Fix some checks in lvm-utils.sh. Note that "$(test ...)" is always empty, since
"test" never prints anything. Therefore, "return $(test ...)" is equivalent to
just "return;" which means success in sh (same as return 0). We can however,
thanks to set -e, use "test foo = bar" as an assertion.

PS: test a == b is invalid syntax. It is either = or -eq: = is textual and -eq
is numeric comparison.