fs_mgr: adapt to new A/B support

In the new A/B partition support suffixes don't have "_". So, fix fs_mgr
code that assumes it has "_"

Bug: 36533366
Test: boot
Change-Id: I0f528cf1e8fecacb1b4ae34f6dc42e18ebe777bb
Signed-off-by: Fernando Lugo <flugo@google.com>
1 file changed