Telephony: Multiparty Call related fix

Block multiple Call switch request to RIL

Sending a call switch request to RIL before receiving
a response for the previous request causes the lower
layers to not respond. Pending responses from RIL
block the call polling in telephony.
CRs-Fixed: 269330, 278014, 282061, 293727, 441309

Change-Id: I078945f7427fdc7b2b26d6563bc117a3dd4fc9c4
(cherry picked from commit 37ec45c237446a92d0aa008788f4da76ffda8708)
(cherry picked from commit c9ad7936c732e65cdd92029709c3afa7d68017fe)
(cherry picked from commit 3f1bbf5b7ba2fcebd3b2f7442545cbd92446d454)