use llrintl when converting double to micro

This avoids rounding error (noticeable on i386).

Backport: firefly
Signed-off-by: Sage Weil <sage@redhat.com>
(cherry picked from commit 80911736bd61b6b88eac0974d24f21c15c5385a4)

Conflicts:
	src/mon/OSDMonitor.cc