casadm: don't cast a float to an int explicitly

If an underflowed float number was casted to an int explicitly, it's value was
rounded to a lower value.

Using `round()` function ensures that the number will be always rounded to a
nearest integer.

Signed-off-by: Michal Mielewczyk <michal.mielewczyk@intel.com>

casadm/Makefile

@@ -83,7 +83,7 @@ CFLAGS    += -Wall -Werror -z relro -z now -fstack-protector -fPIC -Wformat -Wfo
 #
 # Flags for linking
 #
-LDFLAGS    = -z noexecstack -z relro -z now -pie -pthread
+LDFLAGS    = -z noexecstack -z relro -z now -pie -pthread -lm
 #
 # Targets
 #