replmd: Move logic into new replmd_should_apply_isDeleted() function

replmd: Move logic into new replmd_should_apply_isDeleted() function

It's easier to follow the logic involved here when it's split out into a
separate function.

This patch should not alter the existing logic/functionality.

Note the 'else' case is somewhat redundant, but it avoids excessive
whitespace changes to the function. It'll be tidied up in the next
patch.

Signed-off-by: Tim Beale <timbeale@catalyst.net.nz>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>