Turn loop expression into a while-let expression
Turn loop expression into a while-let expression

To make clippy happy _and_ because it is more succinct and easier to read.

Signed-off-by: mulhern <7b51bcf507bcd7afb72bf8663752c0ddbeb517f6@redhat.com>

trgill/stratisd,stratis-storage/stratisd,trgill/stratisd,stratis-storage/stratisd,stratis-storage/stratisd,mulkieran/stratisd,mulkieran/stratisd