Now that QemuSemaphore is implemented through pthread_cond_t only, we can use
QemuCond and QemuMutex to make the code smaller.  Features such as mutex
tracing and CLOCK_MONOTONIC timedwait are supported in qemu-sem naturally.

Signed-off-by: Longpeng(Mike) <longpeng2@huawei.com>
Message-Id: <20220222090507.2028-4-longpeng2@huawei.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>